Thirty-five figures on why clinical trials struggle to enroll, how sites actually perform, what participants know, what patient recruitment costs, and who ends up in studies, including original benchmarks from nine real Meta recruitment campaigns. Every number links to the primary document it came from. No vendor estimates, no uncited round numbers.
Clinical trial recruitment and enrollment statistics are scattered across journals, registries, and surveys, and often repeated without the source. This page collects them in one place. Each section answers one question a coordinator or principal investigator asks when a study is behind. The figures are grouped so the pattern is visible, and each group ends with what it means in practice. Methodology notes and full citations are at the bottom.
The eleven numbers most worth remembering, with the section each one comes from. Full context and primary sources below.
| Figure | What it measures | Source |
|---|---|---|
| ~80% | Clinical trials that fail to meet their original enrollment timeline | JMIR 2020 §1 |
| 2x | How much longer than planned enrollment typically takes, even when the goal is eventually met | Tufts CSDD §1 |
| 19% | Phase 2 and 3 trials that terminated for accrual or closed under 85% of target enrollment | Carlisle 2015 §1 |
| 11% | Sites in a typical trial that enroll zero patients | Tufts CSDD §2 |
| 48% | Sites selected for a trial that under-enroll or enroll no one | Tufts CSDD §2 |
| 55.6% | Cancer patients with no trial available at their institution | Unger, JNCI 2019 §3 |
| 94% | Past participants willing to join another study | CISCRP 2017 §3 |
| $72 vs $199 | Cost per enrolled participant, online versus offline recruitment | JMIR 2020 §4 |
| 80% | Participants who found their study on social media who found it on Facebook | CISCRP 2025 §4 |
| $0.42 | Average cost per link click across nine Meta recruitment campaigns for university studies, 2023 to 2026 | TrialFill §5 |
| 73% | Participants in trials behind 2020 novel drug approvals who were White | FDA 2020 §6 |
The most-cited number in the industry is that most trials miss their enrollment timeline. The registry data behind it is more specific, and in some ways worse: a meaningful share of trials never reach a usable sample at all.
About 80% of clinical trials miss their original enrollment timeline (JMIR, 2020). Roughly nine in ten eventually reach their enrollment goal, but it typically takes about twice as long as planned (Tufts CSDD). Among cancer patients, only 8.1% enroll in a trial, and more than half have no trial available at their institution (JNCI, 2019). To see what enrollment rate your own study needs, use the enrollment rate calculator.
Falling behind is the normal case, not the exception, and the registry analyses show the failure mode is almost always accrual rather than science. The planning assumption that matters is not whether recruitment will be hard but how early you will notice. The free recruitment plan template is built to make that visible from week two. If your study is already behind, enrollment rescue is built for exactly this point.
Talk through a study that's behindThe Tufts Center for the Study of Drug Development produced the only large-scale breakdown of per-site enrollment performance, and its numbers replaced an older rule of thumb that had been repeated for a decade without data behind it.
A site that enrolls half its target is not an outlier. It is the median experience. The sites that beat it are usually the ones that reach beyond their own patient list, which is the entire premise of digital recruitment for research teams. To check whether your own sites are on pace, calculate your enrollment rate per site per month.
See what a recruitment plan includesThe research on why people do not join studies points away from the participant. Most never get the option, and the ones who do are overwhelmingly willing.
The participants exist and most of them are willing. The gap is structural: more than three in four never get a decision to make, and the people who could be asked are outside the site's own patient list. Recruitment that stops at the existing database is working the smallest part of the problem.
Reach beyond your patient listSend your criteria, timeline, and goal. You'll get a recruitment plan back within one business day with budget, channels, and projected cost per inquiry. Free, no obligation.
Two systematic reviews in the Journal of Medical Internet Research and CISCRP's participant surveys give the clearest picture of how online recruitment performs against traditional methods, and where participants actually find studies now.
The evidence points one direction: online recruitment reaches more people, faster, at lower cost per enrollee, and Facebook is where participants actually find studies. The tradeoff is a lower conversion rate, which is solved with a good screener, not by avoiding digital. See how clinical trial advertising works in practice, or the full guide to Facebook ads for clinical trials.
Get a plan with the ad approachPublished cost figures are scarce and usually come from vendors selling something. Below are the two peer-reviewed benchmarks, plus original numbers from TrialFill's own campaigns, pulled directly from Meta Ads Manager rather than estimated.
In studies that compared both, online recruitment cost a median of $72 per enrolled participant versus $199 for offline methods (JMIR, 2020). Facebook recruitment across 35 health studies cost a median of $14.41 per recruited participant (JMIR, 2017). In TrialFill's campaigns for university research studies, the average was $0.42 per click. What a study pays per enrolled participant then depends on how strict the eligibility criteria are, how demanding the visits are, and how quickly the team calls inquiries back.
Clicks are cheap. Enrollments are not, because most of the cost sits after the click: screening, eligibility, and follow-up speed. The useful planning number is cost per pre-screened inquiry, measured weekly. To size your own study, use the recruitment rate calculator, then see the clinical trial advertising cost guide.
Get a cost estimate for your studyThe FDA publishes the demographics of every pivotal trial behind a novel drug approval. The pattern is stable year to year, and it is a recruitment problem as much as a design one.
Representation follows reach. Trials enroll the people who are near the site, already in the system, and already asked. Geographic and language targeting in recruitment advertising is one of the few levers a site controls directly, and it is one of the reasons to use it.
Start a StudyEnter participants still needed, weeks left, and your sites. The free calculator works backward to the recruitment rate per site per month, the number of pre-screened inquiries it takes, and projected ad spend.
It depends on the method and the study. A 2020 JMIR meta-analysis found online recruitment cost a median of $72 per enrolled participant versus $199 for offline methods in studies that ran both. A 2017 JMIR review of Facebook recruitment across 35 health studies found a median of $14.41 per recruited participant. Across nine Meta campaigns TrialFill ran for university research studies from 2023 to 2026, the average cost was $0.42 per link click. Cost per enrolled participant then depends on eligibility criteria, visit burden, and how quickly the study team follows up.
About 80% of clinical trials fail to meet their original enrollment timelines, according to a 2020 JMIR systematic review. Tufts CSDD found that roughly nine in ten trials eventually reach their enrollment goal, but it typically takes about twice as long as planned. In one analysis of 2,579 closed trials, 19% of phase 2 and 3 trials terminated for failed accrual or finished below 85% of target enrollment.
It varies widely by disease area and setting. In cancer, the best-studied area, a 2019 JNCI meta-analysis of 13 studies and 8,883 patients found that 8.1% of patients enrolled in a trial: 15.9% at academic centers and 7% in community settings. More than half of patients (55.6%) had no trial available for their cancer type and stage at their institution.
Across nine Meta campaigns for university research studies from 2023 to 2026, TrialFill paid an average of $0.42 per link click and about $6.35 per 1,000 impressions, with a 1.51% link click-through rate. A 2017 JMIR systematic review of 35 health research studies found a median of $0.51 per click.
Only primary sources are used: peer-reviewed journal articles, the Tufts CSDD report series, CISCRP's published survey decks, FDA reports, and TrialFill's own campaign data exported from Meta Ads Manager (clearly labeled as such). Where a figure is widely repeated without a traceable origin, it was left out. Figures are reported as published; nothing is rounded beyond what the source itself reports.
These figures belong to their original authors; cite the primary source listed above wherever possible. If you reference this compilation, attribute it as: TrialFill, "Clinical Trial Recruitment Statistics," trialfill.com/clinical-trial-recruitment-statistics, updated October 2026. Found an error or a newer figure? Email ryan@trialfill.com and it will be corrected with credit.
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