About ClinicalTrials.gov


What is ClinicalTrials.gov?

ClinicalTrials.gov is a database registry of publicly and privately supported clinical studies on a wide range of diseases and conditions. 1

Who Contributes?

Information is provided and updated by the sponsor or principal investigator of the clinical study and updated throughout the study. 1

  • Founded By 1


    National Institutes of Health


    Food and Drug Administration

  • Maintained By 1


    National Library of Medicine

  • Implementation & compliance 2


    Food and Drug Administration

Timeline of clinicaltrials.gov 3,4


Total number of registered studies


Significant events

What data is in an entry 5

  • NCTID Number

    NCTID icon

    A standardized, unique ClinicalTrials.gov identifier for each trial which can be used to reference the trial through other resources like PubMed.gov.

  • Interventions

    Interventions icon

    A process or action that is the focus of a clinical study. This can include giving participants drugs, medical devices, procedures, vaccines, surveys, education, or interviews.

  • Study Design

    Study design icon

    The investigative methods used in the clinical study. For intervention studies, these include Primary Purpose, Intervention Method, Masking (Blinding), and Allocation.

  • Outcomes

    Outcomes icon

    The planned measurable or observable results listed in the protocol that are important for evaluating the effect of an intervention.

  • Eligibility Criteria

    eligibility criteria icon

    These criteria explain which medical characteristics individuals must meet in order to join a specific clinical trial.

  • Results Database

    eligibility results database

    An overview of the final statistics and registration information for a completed or terminated clinical trial.

Who Uses ClinicalTrials.gov?

About 64,000 unique visitors a day

source: 3
  • Patients & Public
  • Clinical Research
  • Healthcare Provider
  • IRB & Ethics
  • Other
  • 42%

  • 29%

  • 8%

  • <1%

  • ~21%

Other includes: students, educators, librarians, information professionals source: 7

What was ClinicalTrials.gov designed to do? 6

User Groups

  • woman icon on circle

    Patients & Public

  • Microscope icon on circle

    Research community

  • Stethoscope icon on circle


  • Eye icon on circle

    Users of research

  • Scale icon on circle

    IRBs & Ethics

  • Notepad icon on circle

    Medical journal editor

  • Stack of money icon on circle

    Granting agencies

Registry purpose and user group benefits

  • Fulfill ethical obligations to participants and community

  • Information for potential participants & referring clinicians

  • Reduce publication bias against negative results

  • Help editors and others understand the context of study results

  • Promote more efficient allocation of research funds

  • Help institutional review boards (IRBs) determine appropriateness of a research study


The Clinicaltrials.gov API 8

“This API provides a method for creating links to ClinicalTrials.gov or downloading ClinicalTrials.gov data in XML format. Obtain information including a trial's purpose, who may participate, locations, and phone numbers for more details about clinical trials being conducted throughout the United States and in many countries throughout the world. The API uses RESTful calls and responses are formatted in XML.”

Users Can

Link icon

Create links to ClinicalTrials.gov

XML icon

Download data in XML format


  1. ClinicalTrials.gov Background
  2. FDA's Role: ClinicalTrials.gov Information
  3. ClinicalTrials.gov Trends, Charts, and Maps
  4. ClinicalTrials.gov History, Policies, and Laws
  5. ClinicalTrials.gov Glossary of Common Site Terms
  6. ClinicalTrials.gov Why Should I Register and Submit Results?
  7. Zarin, Deborah A. The Role and Importance of Clinical Trial Registries & Results Databases. 2012
  8. Programmable Web: ClinicalTrials.gov API November 2017 R 1.1