Clinical trial registries help families, caregivers, researchers, and clinicians see the scale of medical research. ClinicalTrials.gov listed 585,919 studies with locations in all 51 states and 226 countries and territories as of May 20, 2026. The figures below describe the registry’s growth, posted results, recruiting studies, geographic scope, and study types.
Contents
- How the registry has grown
- Posted results over time
- Recruiting studies and geography
- United States and international participation
- Interventional study types
- What the numbers mean for caregivers
How the registry has grown
ClinicalTrials.gov had 2,119 registered studies by the end of 2000, according to ClinicalTrials.gov Trends and Charts. The year-end total increased to 3,892 in 2001 and 5,270 in 2002. It reached 8,858 in 2003, followed by 12,024 in 2004.
The count then rose to 24,821 studies by the end of 2005 and 35,738 by the end of 2006. By the end of 2007, the registry had 48,287 registered studies. The 2008 total was 65,850, and the 2009 total was 82,858.
The registry passed 100,000 studies in 2010, when the year-end count was 100,202. It had 118,017 studies in 2011, 137,479 in 2012, and 157,907 in 2013. The count reached 181,214 in 2014 and 205,318 in 2015.
The next year-end totals continued upward: 233,103 studies in 2016, 262,278 in 2017, 293,223 in 2018, and 325,732 in 2019. The total was 362,452 by the end of 2020, 399,465 by the end of 2021, and 437,487 by the end of 2022.
ClinicalTrials.gov recorded 477,191 registered studies at the end of 2023 and 520,862 at the end of 2024. The year-end 2025 total was 563,828. The 2026 figure was 585,919 as of May 20, 2026, rather than a year-end total.
| Measurement point | Registered studies | Timing |
|---|---|---|
| 2000 | 2,119 | Year-end |
| 2005 | 24,821 | Year-end |
| 2010 | 100,202 | Year-end |
| 2015 | 205,318 | Year-end |
| 2020 | 362,452 | Year-end |
| 2025 | 563,828 | Year-end |
| 2026 | 585,919 | As of May 20, 2026 |
These totals are registry counts. They do not state how many studies were completed, how many enrolled participants, or how many studies addressed a particular cancer or caregiver concern.
Posted results over time
ClinicalTrials.gov Trends and Charts reported 78,185 studies with posted results as of May 20, 2026. The year-end history begins with 41 studies with posted results in 2008. The count was 1,139 in 2009 and 2,756 in 2010.
The posted-results total reached 4,956 in 2011 and 7,760 in 2012. It rose to 10,853 in 2013, 15,680 in 2014, and 19,481 in 2015. By the end of 2016, 23,666 studies had posted results.
The registry recorded 29,493 studies with posted results in 2017 and 34,152 in 2018. The count reached 40,675 in 2019 and 46,718 in 2020. It was 52,537 in 2021 and 56,561 in 2022.
Posted results totaled 61,624 studies at the end of 2023, 68,453 at the end of 2024, and 75,745 at the end of 2025. The 2026 count was 78,184 as of May 20, 2026 in the year-by-year series, while the registry summary reported 78,185 studies with posted results on that same date. Those two supplied figures differ by one study, so they should be retained as separate reported values rather than combined or reconciled here.
A posted result is not the same thing as a treatment recommendation or proof that an intervention works. For caregivers reading a study record, results are one part of the record alongside eligibility criteria, study status, intervention details, location, and the study’s stated outcomes.
Recruiting studies and geography
As of May 20, 2026, ClinicalTrials.gov had 65,239 recruiting studies. The registry’s recruiting-study breakdown included 19,165 U.S.-only studies, representing 29% of recruiting studies. It included 42,973 non-U.S.-only studies, representing 66%, and 3,101 studies conducted in both the United States and other countries, representing 5%.
| Recruiting-study scope | Studies | Share of recruiting studies |
|---|---|---|
| U.S.-only | 19,165 | 29% |
| Non-U.S.-only | 42,973 | 66% |
| United States and non-U.S. | 3,101 | 5% |
The percentages are the supplied displayed shares and are not a substitute for a new calculation. They provide a broad geographic view: a recruiting study may be limited to U.S. locations, limited to locations outside the United States, or include both.
For a caregiver trying to understand access, the presence of a recruiting study in the registry does not establish that a nearby site is enrolling a specific patient. Site location, eligibility, recruitment status, age requirements, diagnosis, prior treatment, transportation, and caregiver availability can all matter, but the figures supplied here quantify only the registry-wide recruiting categories.
United States and international participation
Across all registered studies, ClinicalTrials.gov reported 166,334 U.S.-only studies, or 28% of the total. It reported 334,624 non-U.S.-only studies, or 57%, and 25,665 studies conducted in both the United States and non-U.S. locations, or 4%.
The registry also listed 59,296 studies for which the geographic category was not provided, or 10% of the total. These categories describe the distribution of registered studies, not the number of participants or the proportion of people receiving an intervention.
The overall registry geography is broad. ClinicalTrials.gov listed study locations in all 51 states and 226 countries and territories. That scope can help explain why a national search may return many records while a local search returns far fewer relevant options. A caregiver’s practical question is usually narrower: whether a study is recruiting, whether the site is reachable, and whether the patient meets its eligibility requirements.
The all-registered-study counts and recruiting-study counts should not be treated as interchangeable. The first describes the geography of the full registry; the second describes the subset identified as recruiting on May 20, 2026. They also use different denominators and therefore answer different questions.
Interventional study types
ClinicalTrials.gov had 447,111 interventional studies, equal to 76% of all registered studies. Within the interventional group, 217,149 were drug-or-biologic studies, while 174,339 were behavioral-or-other studies, according to ClinicalTrials.gov Trends and Charts.
An interventional study evaluates one or more interventions assigned according to a study protocol. The supplied categories show that interventions are not limited to drugs or biologics. Behavioral-or-other studies form a substantial reported category as well, which is relevant to readers looking for research involving support, behavior, care delivery, or other non-drug approaches.
| Reported study classification | Count | Reported share or relationship |
|---|---|---|
| Interventional studies | 447,111 | 76% of all registered studies |
| Drug-or-biologic interventional studies | 217,149 | Within interventional studies |
| Behavioral-or-other interventional studies | 174,339 | Within interventional studies |
The drug-or-biologic and behavioral-or-other counts should not be added to the total registry count. They are categories within the interventional-study figure, and the supplied facts do not provide every possible interventional subcategory or explain the remaining difference.
What the numbers mean for caregivers
Clinical trial statistics can provide context before a family evaluates an individual study. The registry had 585,919 registered studies as of May 20, 2026, including 65,239 recruiting studies and 78,185 studies with posted results in the registry summary. Those counts indicate the size and activity of the registry, not the suitability of any particular study.
The long-term series also shows how the public record expanded: from 2,119 registered studies at the end of 2000 to 563,828 at the end of 2025. Posted results rose from 41 studies at the end of 2008 to 75,745 at the end of 2025. The measurement dates differ between year-end historical points and the May 20, 2026 snapshot, so the figures should be read with those dates attached.
ClinicalTrials.gov receives about 90,000 visitors per day and about 2 million unique visitors every month, according to ClinicalTrials.gov Trends and Charts. These are reported visitor estimates, not counts of patients, caregivers, researchers, or completed searches. They indicate substantial public use of the registry but do not reveal what visitors sought or whether a search led to enrollment.
For caregiver support, the most useful interpretation is therefore practical and limited: registry totals show the size of the available information environment; geographic figures show how widely studies are distributed; recruiting counts identify the scale of the current recruiting subset; and posted-results counts indicate how many records have results available. A specific decision still depends on the individual study record and the patient’s circumstances.