Recruiting research participants comes down to choosing the right channels, writing materials that pass ethical review, and making it easy for people to say yes. The method that works best depends on your study type, budget, and target population, but nearly every successful recruitment effort combines multiple approaches. Here’s what the evidence shows about each strategy and how to put them together.
Compare Channels Before You Commit
Not all recruitment methods perform equally, and the differences are dramatic. A study published in Contemporary Clinical Trials compared five approaches head to head: social media ads, clinical database outreach, community partner referrals, participant referrals (snowball sampling), and hired community recruiters. The results reshape how most people think about recruitment budgets.
Social media advertising converted 100% of referred individuals into enrolled participants and cost roughly $8 per referral, with only a few hours of staff time per week. Clinical databases produced the largest raw number of participants (34% of the final sample) but converted only 36% of people contacted, at $33 per referral and 94 staff hours. Community partner referrals landed in between, enrolling 86% of people referred. Hired community recruiters were the least efficient option: 38% enrollment, nearly $1,845 per referral, and over 1,000 staff hours for training and supervision.
The takeaway isn’t that one channel is always superior. Clinical databases cast a wider net and may reach populations that don’t use social media. Community partnerships build trust with populations that have historically been excluded from research. But if your budget is tight and your timeline is short, social media advertising delivers outsized returns for minimal investment.
What Social Media Ads Actually Deliver
Social media recruitment is cost-effective, but the funnel narrows quickly. A study tracking Facebook ad performance for a telehealth trial found that out of roughly 33,000 users who saw at least one ad, about 10,000 clicked through. Of those clicks, 4.3% completed the screening form, and only 0.3% ultimately signed a consent form and enrolled. That meant 32 enrolled participants from nearly 10,000 clicks.
Those numbers aren’t discouraging if you plan for them. The cost per click on Facebook remains low, so even a 0.3% conversion rate can be affordable at scale. The key is designing your screening process to minimize friction. Every extra step between ad click and screening form completion loses people. Link directly to a short eligibility screener, keep the form under two minutes, and follow up with eligible respondents within 24 to 48 hours.
Direct Patient Outreach Beats Passive Referral
If your study involves a clinical population, reaching patients directly through electronic health portals significantly outperforms waiting for physician referrals. A JAMA Oncology study compared two approaches: sending patients a portal message about a trial versus relying on standard-of-care physician referrals. In the portal message group, 35% of patients responded and 20% enrolled. In the physician referral group, just one patient (0.5%) was referred and none enrolled.
The lesson is straightforward. Physicians are busy and rarely remember to mention studies during appointments. A direct, well-written message to eligible patients removes that bottleneck entirely. If you have access to a clinical database or patient portal, use it as a primary channel rather than counting on clinicians to make referrals on your behalf.
Recruiting Underrepresented Populations
Recruiting participants from historically underrepresented groups requires a trust-first approach. Communities that have experienced exploitation in research, or that simply lack exposure to clinical studies, won’t respond to a cold social media ad the same way other populations might. The most effective framework is community-based participatory research, where academic teams and community organizations collaborate as genuine partners from the start.
In practice, this means showing up before you need anything. Attend local events, offer free health services like blood pressure screenings, and provide bilingual materials when relevant. Once a relationship exists, ask respected leaders within trusted local organizations to help spread the word about your study. This kind of recruitment takes longer, but it produces participants who are more likely to stay enrolled because the relationship is built on reciprocity rather than transaction. After the study ends, share your findings with the community. That step preserves the partnership for future work.
The FDA has formalized the importance of diverse enrollment. Under the 2024 draft guidance on Diversity Action Plans, sponsors of drug, biologic, and medical device studies are now expected to submit plans describing how they will improve enrollment of underrepresented populations. Even if your study isn’t FDA-regulated, building demographic diversity into your recruitment strategy strengthens both your data and your ethical standing.
Specialized Recruitment Platforms
Several online platforms exist specifically to connect researchers with willing participants. ResearchMatch, for example, is a volunteer registry that has been operating since 2010. People sign up because they want to be contacted about studies. Researchers can filter the registry by key eligibility criteria and send IRB-approved recruitment messages directly through the platform. ResearchMatch is designed for clinical and translational health research, so it’s not appropriate for behavioral or social science studies that fall outside health topics.
For non-clinical research, platforms like Prolific and CloudResearch specialize in recruiting participants for surveys and online experiments. These platforms maintain large, diverse participant pools and allow researchers to set demographic filters. They handle compensation automatically, which removes a significant administrative burden. If your study can be completed online, these platforms can fill a sample within hours rather than weeks.
Writing Recruitment Materials That Get Approved
Your recruitment ad or flyer needs to pass IRB review before anyone sees it. The FDA provides clear guidance on what’s acceptable: ads should contain only the information a prospective participant needs to determine eligibility and interest. That includes the researcher’s name and contact information, the condition or topic under study, a summary of eligibility criteria, the time commitment required, the study location, and a brief mention of benefits like a no-cost health exam.
What you can’t do matters just as much. Never describe an investigational drug or device as a “new treatment” or “new medication” without stating that it’s investigational. Don’t promise “free medical treatment” when you mean participants won’t be charged for study procedures. Don’t claim the intervention is safe or effective, because that’s exactly what you’re trying to determine. If your study offers compensation, you can mention it, but don’t emphasize the dollar amount through bold text or large font. IRBs interpret that as potentially coercive.
On the creative side, label your study clearly as research. Use phrases like “research study” rather than just “study,” and include your institutional affiliation. Provide complete contact details: investigator name, title, department, and institution. These elements signal legitimacy and help your materials clear IRB review on the first submission.
Setting Fair Compensation
Compensation should reflect the time and inconvenience you’re asking of participants without crossing into coercion. A commonly cited benchmark from institutional guidelines is $25 per hour for studies involving more than minimal risk, based on the time participants spend preparing for, taking part in, and recovering from research procedures. Your IRB has the authority to adjust that rate up or down based on the specifics of your protocol.
Beyond hourly pay, consider covering travel costs and providing meal vouchers for in-person visits. These practical gestures reduce barriers to participation and improve retention over time. If total compensation for any participant is likely to exceed $600 in a calendar year, your consent form must note that an IRS 1099 form will be issued. This is a detail that’s easy to overlook and can delay IRB approval if missing.
Keeping Participants Once You Have Them
Recruitment means nothing if participants drop out before your study ends. Retention in long-term trials depends on consistent, low-effort communication. Phone call reminders, text messages, and emails before each scheduled visit are the most commonly used and effective techniques. Some research teams also send birthday or anniversary cards, which sounds minor but reinforces the participant’s sense that they matter as a person, not just a data point.
Financial mechanisms help too. Reimbursing travel at each visit (rather than in a lump sum at the end) gives participants a reason to keep showing up. Providing free medical investigations and covering the cost of any medications taken as part of the study removes financial anxiety that might otherwise push someone to withdraw. The principle behind all of these strategies is the same: every interaction should make participation feel easy and valued.