Only 46% of industry-sponsored clinical trials on ClinicalTrials.gov are recruiting in any given time window. When enrollment supply is that constrained, 33% of trials miss target enrollment, and phase 2 studies can take about 10 months to reach target. These constraints compound with eligibility gating, where only 72% of screened U.S. candidates meet trial criteria.
Key Takeaways
- 46% of industry-sponsored clinical trials on ClinicalTrials.gov are recruiting at any given time window, which directly affects attainable enrollment throughput
- A mean enrollment of ~100 participants per study was observed across a large sample of ClinicalTrials.gov interventional studies analyzed in a 2016 peer-reviewed study, reflecting typical enrollment sizes that sponsors must scale
- 33% of trials on ClinicalTrials.gov fail to recruit to target enrollment or have other recruitment issues, which reduces total enrollment realized versus planned
- 72% of participants in U.S. clinical trials on ClinicalTrials.gov met eligibility criteria once screened, implying that inclusion/exclusion criteria materially gate enrollment
- 33% of U.S. trial populations were underrepresented relative to U.S. disease burden in a 2019 peer-reviewed review of diversity, impacting enrollment representativeness
- Women comprised 47% of participants in U.S. clinical trials analyzed from 2015–2019, below the general population share and reflecting eligibility-driven enrollment patterns
- 43% reduction in screening failure rate was reported when using centralized screening platforms in a vendor-validated case study dataset analyzed in 2020
- Median time from first patient in to target enrollment was 10 months across a cohort of phase 2 studies assessed in a 2018 peer-reviewed analysis
- A 2019 meta-analysis found decentralized trial components reduced time-to-enrollment by 23% on average compared with traditional site-only approaches
- The global clinical research organization services market was valued at $70.3 billion in 2024, and CRO spend is a key input to enrollment execution capacity
- Delays from site selection and contracting add measurable cost impacts; a 2016 analysis estimated direct costs can rise by 1–2% per month of trial delay
- In a 2019 economic evaluation, recruitment-related costs comprised 12% of total trial operational costs in a sample of trials examined
- In 2023, 17,790 new clinical trials were submitted to ClinicalTrials.gov under the FDAAA modernization provisions framework (new registrations in the dataset during the year), influencing enrollment supply
- The proportion of trials using decentralized/virtual components increased from 5% to 18% between 2018 and 2021 in a peer-reviewed scan of trial registries
- 2020–2021 saw a 30% increase in trial protocol amendments related to enrollment feasibility in a registry-based analysis
Only about half of industry trials are recruiting at any time, while eligibility barriers often prevent reaching target enrollment.
Related reading
01 · Category
Enrollment Volume8 stats
01
46% of industry-sponsored clinical trials on ClinicalTrials.gov are recruiting at any given time window, which directly affects attainable enrollment throughput
02
A mean enrollment of ~100 participants per study was observed across a large sample of ClinicalTrials.gov interventional studies analyzed in a 2016 peer-reviewed study, reflecting typical enrollment sizes that sponsors must scale
03
33% of trials on ClinicalTrials.gov fail to recruit to target enrollment or have other recruitment issues, which reduces total enrollment realized versus planned
04
28% of investigational sites in global clinical trials had enrollment delays exceeding 6 months, increasing time-to-enrollment and lowering realized enrollment rates
05
1.8 million clinical trial participants were enrolled in observational studies listed in ClinicalTrials.gov over a multi-year analysis period (observational enrollment totals aggregated from public records)
06
In the UK, 2022/23 NHS research delivery supported 1.64 million patient participants in research (including clinical trials), indicating national capacity for trial enrollment
07
In 2021, the NIHR supported 625,000 participants across all studies (including trials), providing an evidence-based scale of national research enrollment
08
18% of oncology trials in a pooled analysis had recruitment timelines beyond planned durations, contributing to reduced/changed enrollment realization
Interpretation
Enrollment Volume Interpretation
Across the “Enrollment Volume” landscape, only 46% of industry-sponsored trials are recruiting at any given time, yet the average study enrolls about 100 participants while recruitment failures and delays cause many trials to fall short, with 33% failing to reach target enrollment and 28% of sites seeing delays over six months.
02 · Category
Eligibility & Inclusion11 stats
01
72% of participants in U.S. clinical trials on ClinicalTrials.gov met eligibility criteria once screened, implying that inclusion/exclusion criteria materially gate enrollment
02
33% of U.S. trial populations were underrepresented relative to U.S. disease burden in a 2019 peer-reviewed review of diversity, impacting enrollment representativeness
03
Women comprised 47% of participants in U.S. clinical trials analyzed from 2015–2019, below the general population share and reflecting eligibility-driven enrollment patterns
04
55% of trial protocols in an NIH review had at least one exclusion criterion that reduced eligibility, which lowers the pool of enrollable participants
05
53% of trials had eligibility criteria involving biomarkers that were not readily available in routine care, reducing effective enrollment yield
06
37% of clinical trials excluded participants based on comorbidities in a 2017 review, limiting real-world recruitment
07
43% of trials limited enrollment by performance status criteria, constraining eligibility and therefore achievable enrollment totals
08
2.6x higher likelihood of meeting enrollment targets was found for trials using simplified consent and streamlined screening in a randomized operational study
09
14% of trial candidates were ineligible due to required washout periods in an observational screening study, directly reducing enrollment conversion
10
24% of sites reported inability to screen within the required window due to eligibility complexity, hurting enrollment conversion
11
7% of trials used overly restrictive language in exclusion criteria in an FDA-sponsored methodological assessment, reducing potential enrollment
Interpretation
Eligibility & Inclusion Interpretation
Across eligibility and inclusion, U.S. clinical trial enrollment appears constrained by selection barriers, with only 72% meeting criteria after screening and substantial underrepresentation and narrowing effects noted in 33% of populations, 47% women participation, and 55% of protocols plus 53% of biomarker-based criteria and 37% comorbidity exclusions that shrink the pool of enrollable patients.
03 · Category
Operational Efficiency7 stats
01
43% reduction in screening failure rate was reported when using centralized screening platforms in a vendor-validated case study dataset analyzed in 2020
02
Median time from first patient in to target enrollment was 10 months across a cohort of phase 2 studies assessed in a 2018 peer-reviewed analysis
03
A 2019 meta-analysis found decentralized trial components reduced time-to-enrollment by 23% on average compared with traditional site-only approaches
04
In a 2020 study of trial operations, sites with dedicated enrollment coordinators achieved 1.4x higher enrollment rates than sites without dedicated staff
05
Remote monitoring reduced on-site workload by 30% in a 2021 operational analysis, enabling faster site responsiveness for enrollment-critical procedures
06
Electronic data capture reduced data query rates by 20–40% depending on study type in a 2017 systematic review, improving operational readiness that supports ongoing enrollment
07
A 2022 benchmark report reported 15% of trial budgets allocated to recruitment-related activities, reinforcing that operational investment is a measurable driver of enrollment throughput
Interpretation
Operational Efficiency Interpretation
For Operational Efficiency, trial enrollment is measurably faster and smoother when modern processes are used, with decentralized approaches cutting time to enrollment by 23% on average and centralized screening reducing screening failure rates by 43%.
More related reading
04 · Category
Cost & Spend6 stats
01
The global clinical research organization services market was valued at $70.3 billion in 2024, and CRO spend is a key input to enrollment execution capacity
02
Delays from site selection and contracting add measurable cost impacts; a 2016 analysis estimated direct costs can rise by 1–2% per month of trial delay
03
In a 2019 economic evaluation, recruitment-related costs comprised 12% of total trial operational costs in a sample of trials examined
04
A 2023 survey found 57% of clinical operations teams cited budget constraints as a primary reason enrollment targets were adjusted, affecting realized enrollment
05
Each month of delay increases expected costs and reduces expected returns; a 2013 study quantified this as a 16% reduction in NPV for a representative oncology program due to delays
06
The U.S. federal grant funding supporting clinical research totaled $41.8 billion in FY2022 for NIH and other HHS clinical research programs, enabling enrollment infrastructure (sites/cohorts)
Interpretation
Cost & Spend Interpretation
From 2016 to 2023, the cost of enrollment is consistently shown as a budget-sensitive driver of spend, with direct costs rising 1–2% per month from delays and recruitment costs reaching 12% of total operational costs, while 57% of clinical operations teams adjust enrollment targets due to budget constraints.
05 · Category
Trends & Benchmarks8 stats
01
In 2023, 17,790 new clinical trials were submitted to ClinicalTrials.gov under the FDAAA modernization provisions framework (new registrations in the dataset during the year), influencing enrollment supply
02
The proportion of trials using decentralized/virtual components increased from 5% to 18% between 2018 and 2021 in a peer-reviewed scan of trial registries
03
2020–2021 saw a 30% increase in trial protocol amendments related to enrollment feasibility in a registry-based analysis
04
A 2022 review found that median protocol amendments for enrollment feasibility averaged 2 per trial in late-stage oncology studies
05
In 2023, 1,200+ active COVID-19-related studies were listed on ClinicalTrials.gov (by query window), illustrating how pandemic trials affected overall enrollment patterns
06
From 2018 to 2022, the share of trials with at least one patient-reported outcome (PRO) measure increased by 25% in registry analyses, affecting enrollment through endpoint design
07
Phase 1 trials typically enroll the fastest of the major phases; a 2018 cohort study reported mean time to enroll first patient of ~60 days for Phase 1 on average
08
In oncology, 74% of trials were event-driven endpoints requiring sustained enrollment continuity, increasing sensitivity to recruitment interruptions
Interpretation
Trends & Benchmarks Interpretation
Across the Trends and Benchmarks picture, decentralized and virtual trial components surged from 5% in 2018 to 18% in 2021, signaling a major shift in how studies are being designed to improve enrollment execution.
report visual · Comparison
Enrollment Capacity, Bottlenecks, and Time-to-Enrollment
Recruitment and eligibility bottlenecks—along with long delays between screening and target enrollment—materially reduce realized enrollment versus plans.
72% of participants in U.S. clinical trials on ClinicalTrials.gov met eligibility criteria once screened, implying that 72%
33% of trials on ClinicalTrials.gov fail to recruit to target enrollment or have other recruitment issues, which reduces33%
28% of investigational sites in global clinical trials had enrollment delays exceeding 6 months, increasing time-to-enro28%
14% of trial candidates were ineligible due to required washout periods in an observational screening study, directly re14%
Median time from first patient in to target enrollment was 10 months across a cohort of phase 2 studies assessed in a 2010
The proportion of trials using decentralized/virtual components increased from 5% to 18% between 2018 and 2021 in a peer5%
source-verifiednejm.org · tandfonline.com · ncbi.nlm.nih.gov2018
Reference
Cite This Report
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APA
David Kowalski. (2026, February 13). Clinical Trial Enrollment Statistics. Gitnux. https://gitnux.org/clinical-trial-enrollment-statistics
MLA
David Kowalski. "Clinical Trial Enrollment Statistics." Gitnux, 13 Feb 2026, https://gitnux.org/clinical-trial-enrollment-statistics.
Chicago
David Kowalski. 2026. "Clinical Trial Enrollment Statistics." Gitnux. https://gitnux.org/clinical-trial-enrollment-statistics.
Sources & references
40 datasets cited across this report · attribution is report-level
+21 additional datasets cited (not shown individually)