# ClinicalTrials.gov Classic API

**Canonical:** https://apis.io/apis/clinical-trials-gov/classic-api/  
**Provider:** ClinicalTrials.gov — https://apis.io/providers/clinical-trials-gov/  
**Base URL:** https://clinicaltrials.gov/api  
**Documentation:** https://clinicaltrials.gov/data-api/api

ClinicalTrials.gov Classic API is one of 6 APIs that [ClinicalTrials.gov](https://apis.io/providers/clinical-trials-gov/) publishes on the [APIs.io](https://apis.io/) network. Tagged areas include Clinical Trials, Legacy, and REST. The published artifact set on APIs.io includes API documentation.

The Classic API is the legacy ClinicalTrials.gov interface that preceded the Data API v2 and exposes full-study, brief-study, and field-values endpoints with XML, JSON, and CSV responses. It is being deprecated in favor of the v2 REST API and remains online for backward compatibility while consumers migrate.

## Machine-readable artifacts (2)

- **Documentation** — https://clinicaltrials.gov/data-api/api
- **APIsJSON** — https://raw.githubusercontent.com/api-evangelist/clinical-trials-gov/refs/heads/main/apis.yml

## Other ClinicalTrials.gov APIs (5)

- [ClinicalTrials.gov Bulk Downloads](https://apis.io/apis/clinical-trials-gov/bulk-downloads/)
- [AACT Database](https://apis.io/apis/clinical-trials-gov/aact/)
- [ClinicalTrials.gov Stats API](https://apis.io/apis/clinical-trials-gov/clinical-trials-gov-stats-api/)
- [ClinicalTrials.gov Studies API](https://apis.io/apis/clinical-trials-gov/clinical-trials-gov-studies-api/)
- [ClinicalTrials.gov Version API](https://apis.io/apis/clinical-trials-gov/clinical-trials-gov-version-api/)

## Tags

Clinical Trials, Legacy, REST

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/apis/clinical-trials-gov/classic-api/). The API's provider profile, Kin Score and agent-readiness rating are at https://apis.io/providers/clinical-trials-gov/.