Clinical Trials Registry (NIH)

ClinicalTrials.gov is a service of the United States National Library of Medicine at the National Institutes of Health and functions as a global public registry and results database for clinical studies in humans. It is designed to improve clinical trial transparency by making key information on study design, conduct and results accessible to patients, health professionals, researchers and regulators, and by assigning each registered study a unique National Clinical Trial (NCT) number. It has global coverage as registered studies are from many countries around the world. As one of the major international trial registries, it increases global transparency of clinical research by providing public access to registration data, results and, where available, key study documents. Investigators can consult statistical analysis plans and protocols from comparable trials to inform their own study design and analysis planning.

Landing page and core user workflows
The landing page presents two main workflows: “Find Studies” for users who want to search and review information on clinical studies, and “Submit Studies” for sponsors and investigators who need to register trials and submit results through the Protocol Registration and Results System. “Find Studies” offers a basic search box and advanced filters (for example condition or disease, intervention, location and recruitment status), plus an expert search interface, while “Submit Studies” links to account management, help resources and training materials for data submitters.

Study Basics and patient resources
The “Study Basics” area provides introductory information explaining what clinical studies are, how they are designed and what participation involves, helping users understand concepts such as study phases, randomisation and eligibility. Within this section, the “Patient Resources” page offers curated links to trusted external resources on research participation, protection of research volunteers, Food and Drug Administration oversight of drugs and devices, and condition‑specific trial information (for example cancer, cardiovascular disease, genetic and rare diseases, HIV/AIDS, COVID‑19). These materials support patients, families and carers in understanding potential benefits and risks, questions to ask and how to find and evaluate clinical trial options.

Policies and intended use
Policy and information pages describe the intended use of ClinicalTrials.gov and the regulatory context for registration and results reporting, including relevant United States requirements and international transparency standards. They explain who is responsible for submitting study information, which types of studies may be listed, what data elements are required and how records are reviewed and updated, and provide links to detailed guidance, help documents and frequently asked questions for both the public and submitters. These sections emphasise that ClinicalTrials.gov is an information resource to support discussions with health care professionals, rather than a source of medical advice or treatment recommendations.

Data and API
The “Data and API” area explains how users can access ClinicalTrials.gov data programmatically or as downloadable files. It describes the ClinicalTrials.gov application programming interface (API), the organisation of available fields and formats, and provides links to the OpenAPI specification and technical documentation for developers. Additional pages show how to download study record data directly from the site in formats such as CSV and how to work with study data in Health Level 7 (HL7) Fast Healthcare Interoperability Resources (FHIR) format, supporting large‑scale analysis and integration with other data systems.