At some point during the fall of 2005, Brian Stone grew tired of throwing up in a bucket and decided to go rogue.

Stone (who requested that his real name not be used) was doing his vomiting three days a week at an inpatient clinical-trial site in his hometown of Columbus, Ohio, following a tip he’d gotten from a stranger at a bar. “He had quite a few to drink,” Stone recalled, “and he was yakking about a place where he could get paid $2,500 just to do painkillers and drink alcohol. And everyone was laughing at him, like, ‘You’re full of shit.’”

As it turned out, he wasn’t. At the time, Stone was unhappily working a hodgepodge of part-time restaurant and factory jobs. Intrigued by the promise of an easier way to make money, he enrolled as a guinea pig in a four-week study testing the effects of alcohol on a painkiller drug.

“It was pretty harsh,” he said. Many of the participants became violently ill; Stone vomited while having his blood drawn. The clinic staff told participants to use a bucket rather than the toilet, if possible, so that they could look through the vomit to see how much of the pill had been digested before it came back up. After the first round, Stone said, he began sneaking into the bathroom after each dose and forcing himself to throw up the pill, to stave off the side effects. The staff didn’t catch on, he told me, and he didn’t share his trick with any of the other participants. “I figured I could get away with it if I kept my mouth shut.”

At the end of the four weeks, he collected his $2,500 and vowed never to do another trial again.

It was a promise that didn’t last very long. Soon afterwards, Stone did a second study, this time for a diabetes drug. The second experience was the opposite of his first, he said, with no side effects: Just swallow a pill and relax in between blood draws and blood-pressure tests. He began looking up the numbers for clinics in Ohio, Indiana, and Michigan, calling regularly to learn about upcoming tests. At each one, he networked, befriending other participants who told him about new opportunities. He quit his jobs. He moved to Austin, where trial sites are more plentiful than they are in Columbus.

Today, Stone no longer relies on strangers in bars—instead, he’s a part of a small community that shares info about study opportunities. Stone says he sends mass texts whenever he sees a new study online. In exchange, the group does the same for him. The members of this group call themselves guinea pigs, or lab rats. They also call themselves professionals.

* * *

There are a few things most serious guinea pigs eventually learn. The first is: There’s such a thing as being too honest.

When Robert Helms, a former union organizer and now-retired guinea pig from Philadelphia, began doing studies in the early 1990s, other guinea pigs he knew from around the neighborhood “drilled me on what to say and what not to say,” he said. “Basically, it’s ‘Have you ever been sick a day in your life?’ ‘Has anyone you’ve related to ever been sick a day in their life?’ And the general answer is no.”

For studies looking for healthy subjects, the screening process generally comes in two steps. The first is over the phone, when guinea pigs call to express their interest. “A lot of places will ask if you’ve ever smoked a cigarette even once,” Stone said. “And if you say yes, boom, that’s the end of it. Sometimes you have to skirt around it.”

The second step is in person, where clinic staff will check blood, urine, and vital signs to determine whether subjects’ claims are true. Some studies, the well-paying ones, are competitive, and clinics will often admit more people than they need from the phone screen, expecting to cull the herd after the round of physicals. Pros know to avoid alcohol and drugs in the days leading up to the screening. Some of the more cautious ones will also abstain from exercise, out of worry that an increased creatinine level will make it appear as though they’ve been drinking.

Clinics will also ask about the so-called “washout period,” the 30-day window most clinics require in between when a person last participated in a study and when they can begin a new one. It’s a twofold purpose: protect the health of the subjects, and protect the integrity of the data.

There are some companies, like Verified Clinical Trials, that track participation across trial sites; researchers can subscribe to make sure their subjects aren’t enrolled in more than one study at the same time, or haven’t been in one too recently. Often, though, clinics rely on the participants themselves to enforce the washout.

“Usually you’ll say, ‘I haven’t been in a study since the last time you saw me,’ or ‘I was in one last year in such and such a place,’” Helms said. “They all keep separate lists and it only very rarely crosses over, [like] when a nurse who happens to work in two places takes a shift at a different place.”

“It sounds selfish,” Helms said of the deception, “but the way it works is, I’m working poor, and the people making the drugs are filthy rich, and I need a job.”

Depending on when it happens, getting caught in a lie can either get a participant bounced from a study, or it can cause a company to scrap the whole thing. “It really jeopardizes the science and the integrity of the data you’re going to gather,” said John Lewis, the vice president of public affairs at the Association of Clinical Research Organizations. “If you go back and you find people who violated that or were not honest … then you’re potentially throwing out their data and maybe the whole study,” at a potential cost of millions of dollars.

But Helms believes the risk to companies comes with a trade-off: Professionals may lie their way into a study, he says, but they also make it run more smoothly. “They need people who are reliable. Pro guinea pigs, we come where we’re supposed to be on time, we’re not afraid of needles. When you explain something it’s going to be understood because you know what’s going on,” he said. “It’s not going to be a disaster. The way disasters happen is when a guy comes in and he doesn’t know the ropes.”

* * *

In chronological order, the phases of drug testing work like this: Phase 1 studies, which test for safety, typically use between 20 and 80 healthy subjects to determine a drug’s side effects and how it’s metabolized in the body. Assuming the drug proves safe, it then advances into Phase 2, which measures its effectiveness against another treatment or a placebo; this time, the study participants are patients with whatever condition the drug was developed to treat, usually somewhere between a few dozen and a few hundred. Phase 3, the last phase before the drug is submitted to the FDA for approval, can include hundreds or thousands of patients and measures both safety and efficacy, as well as how the drug behaves in different types of patients or in conjunction with another therapy.

For professional guinea pigs, Phase 1 trials are almost always where the money is. Some are run out of hospitals or universities, but more often, they’re run by contract research organizations (CROs), groups that the sponsoring pharmaceutical companies pay to handle everything from the institutional review board through to dosing the subjects.

Many CROs maintain their own trial sites for inpatient studies, housing and feeding participants for the duration of the trial. Accommodations at these sites are generally dorm-style, often with a handful of people bunking up in the same room. Food varies widely in both source and protocol: Studies can be catered or rely on an in-house kitchen, and may require participants to finish their meals or track how much they leave over. Some sites supply computers, TVs, or reading material; at others, guinea pigs are in charge of providing their own entertainment. (When I spoke to Stone, he was at a site that had a pool table and video games, but he told me he was planning to ignore both and spend the time brushing up on his Spanish.)

Phase 1 studies are also the least regulated. Companies aren’t legally required to register a trial with, the database maintained by the NIH, until it reaches Phase 2. “It seems to me like if you were considering signing up for one of these things, you would at least want to know the data that’s out there about [safety],” said Carl Elliott, a bioethics professor at the University of Minnesota who has written extensively on the ethics of human-subject research. “[But] since it’s not on, you can’t.”

In 2001, Elliott co-authored an editorial titled “Justice for the Professional Guinea Pig,” arguing for an overhaul of the way human subjects are treated. “Studies on healthy subjects—unlike research on sick patients—are best characterized as a kind of labor relations,” he wrote. Among other things, he argued that participants should be able to negotiate payment based on the discomfort they experience during a study.

“Under the basic ethics guidelines … research subjects are treated as if they are altruistic volunteers,” he told me. The issue of payment for research participation is an especially complicated one, and the pretense of altruism acts as a hedge against accusations of unethical behavior. “You have to ask: Who has a month or three weeks to just check in to a trial site or live there for that amount of time?” he said. “Homeless people, undocumented people, people who are either temporarily or long-term unemployed, people who are out of jail who can’t get regular work.” Paying members of vulnerable groups to put experimental drugs in their bodies can seem dangerously close to coercion.

But treating money as an afterthought rather than the main motivator also means that guinea pigs aren’t considered employees. “It’s work, but it offers none of the protections of work,” Elliott said. “You don’t have the right to minimum wage, you don’t have the right to unionize, you don’t have disability payments, you don’t even have regular health and safety inspections.”

At least once, Helms has tried to solve some of these problems on a smaller scale. In late 2002 he was enrolled in a study for an anti-anxiety drug that was supposed to end before the holiday season. Because of various delays, the researchers ended up extending the trial until after Christmas—the participants would be let out for a break, but they couldn’t consume any alcohol, a condition that upset some people hoping to drink over the holidays.

“It never occurred to them that when you screw up somebody’s holiday after you agree to the price, you’re making it a completely different deal,” he said. This, coupled with the fact that the study was a particularly unpleasant one involving feces collection, was enough to push them into action.

Helms knew some of the other participants well from past studies, and all agreed that the promised $3,350 fee was too low, considering how the trial had shaped up. Helms suggested they swallow scraps of fabric that read “more money,” leaving the investigators to find the notes in their feces. Instead, they took a less dramatic approach, presenting clinic staff with a signed petition. It worked: On the night before the holiday break, the researchers told the group that they’d gotten permission from the sponsoring drug company to raise their pay by $800.

For Elliott, money is less of a concern than safety. It’s impossible to talk about human medical research in the U.S. without mentioning the Tuskegee syphilis experiments, or the widespread use of prisoners as Phase 1 subjects that lasted from the 1940s through the 1970s. Today’s system is, in theory, supposed to catch and prevent those types of abuses—IRBs review trial materials to ensure informed consent and participant safety, and the FDA can inspect the living conditions at trial sites—but the system has had its own major failures. In 2005, Bloomberg published a scathing indictment of the clinical-trial industry, detailing the filthy conditions of a trial site in Miami that had been converted from a Holiday Inn. Almost all the residents were poor immigrants.

Just because the FDA can inspect a site, as the Miami site demonstrated, doesn’t necessarily mean it will. “[Inspections] couldn’t possibly happen with every trial. If you look at food safety, the FDA doesn’t inspect every cantaloupe that comes from Mexico. They just can’t,” Lewis said.

And the IRB process, Elliott said, has its own problems. Many IRBs are for-profit businesses hired by CROs and drug companies, which means “you’re essentially paying an oversight body to approve your study. The incentives to make it easy on the research sponsors are pretty dramatic,” he said. University IRBs, which can involve one colleague reviewing another’s study, aren’t foolproof either.

“Neither of those makes sense,” he said. “You’ve got to have some kind of independent oversight body without those conflicts of interest.”

* * *

Another on-the-job lesson: In guinea-pigging, cooperation can go a long way.

Paul Clough runs the website Just Another Lab Rat, a one-stop shop for all things guinea pig. The site has a continually updated list of upcoming studies around the country, a glossary of common lab tests, tips for getting into studies (“If your blood pressure is usually at the upper threshold, a daily intake of garlic can help”), and even a packing guide. (Phones with cameras are usually allowed, but the cameras may be covered with tape; slippers are a plus, since participants may be forbidden from going barefoot in case there’s a needle on the floor.)

It also has a message board where users can arrange carpools, arrange meetups by region, or review certain companies’ accommodations. In one post, for example, a user praised a clinic’s recent upgrade: “They bought brand-new recliners which are super comfy and every one can have one to themselves. Their food is now being catered by Hyvee (a local grocery and popular chain) and their food is really good.” Others compliment or condemn clinics’ check-in systems or entertainment options.

Clough, who supplements his income from studies by running ads on his website, has a story similar to Stone’s. In 2004, he was in Kansas City in between jobs—“construction, cleanup, back-breaking work,” he said. During a trip to the library, he struck up a conversation with a stranger who told him he knew of a quick, easy way to make money. Following the man’s advice, Clough found and enrolled in his first study, $600 for three nights. As soon as he was out, he began researching all he could. He also moved to Austin, “a hot spot for trials,” in 2004, and founded Just Another Lab Rat the next year.

“I already had all this data compiled … all the information is out there, I just put it in one place,” he said. Just Another Lab Rat also had a print precursor, although one with more of an activist edge: In the mid-‘90s, Helms began curating historical tidbits, bioethics discussions, and reviews of trial sites into a zine he called Guinea Pig Zero.

But for all the shared resources and carpools, the world of guinea pigging is also cutthroat. Some of the more lucrative studies can fill up within minutes, Stone told me. Well-paying gigs can be hard to come by. Full-time guinea pigs typically make somewhere between $15,000 and $40,000 a year. Stone, Clough, and Helms have all supplemented their income from studies with odd jobs or, in Clough’s case, the website.

“If there’s enough money, you’ll throw your standards out the window for it,” Stone said. He won’t do anything that involves opiates—unless the price is right.

That’s where his text-message network comes in. Implicit among the group members is the promise that they will share news of the best studies between them, ideally registering en masse before too many others see the opportunity. “It’s a ‘scratch my back, I scratch yours’ type situation. If I send information to somebody [about a study] but they don’t send it to me, I’m going to cut them off pretty quick.”

Even making it into the study isn’t a guarantee. “A lot of times, people narc on each other” when someone has fibbed their way into a trial, Clough said. “People get together on the outside, you piss off somebody, they go narc on them when they’re in the clinic and get them kicked out.”

* * *

A final guinea-pig lesson: It can be a title, or it can be a dirty word.

The first use of “guinea pig” as “human subject of an experiment,” according to the Oxford English Dictionary, was in 1913, when George Bernard Shaw decried “the … folly which sees in the child nothing more than the vivisector sees in a guinea pig: something to experiment on with a view to rearranging the world.”

At the time, actual guinea pigs were in the height of their popularity as research subjects. The animals, a laboratory staple through the 19th and early 20th centuries, played a role in medical breakthroughs ranging from the discovery of vitamin C to the development of Pap smears. In the mid-1900s, guinea pigs began to fall out of use, replaced by rats and mice. Over time, the term “guinea pig” in a lab context became more strongly associated with people—for better or for worse.

As Daniel Engber wrote in a history of the term for Slate in 2012:

To call someone or something a guinea pig may suggest a mere experiment (“Joe Biden was put out as a guinea pig for the White House”), or it can invoke the specter of exploitation (the U.S. Army wanted “to use young men as guinea pigs and throw them away”). The image either describes the scientific process or condemns it. It's a totem or a scarecrow.

To many who do it full-time, it’s the latter. As the operator of Just Another Lab Rat, Clough is a very public face of the profession, but he said he knows plenty of others who are less open about what they do: “It’s kind of a dirty secret,” he said. “I know one guy who tells his family he’s a computer salesman, and that’s why he travels around the country.”

Stone’s family thinks his guinea pigging is a side gig, something he does on weekends around some other, more traditional job.

Among his friends, though, he’s more open: “It would be pointless to hide it,” he said. “All my friends are guinea pigs.”