The MONDO disease ontology gives each disease one identifier and connects it to the codes used by OMIM, Orphanet, ICD, NCIt and other systems. Here is how to search and download MONDO, how its mappings work, and how ClinicaLister uses it so a search for a disease finds trials registered under any of its names or subtypes.
Mondo aims to harmonize disease definitions across the world. Many disease vocabularies exist — OMIM, Orphanet, the Disease Ontology, NCIt, ICD, MedDRA, SNOMED CT and others — and each describes diseases differently. Mondo is a semi-automatically built ontology that merges these resources into one hierarchy with a stable MONDO identifier per disease, for example MONDO:0008903 for lung cancer.
Its mappings go beyond loose cross-references: Mondo curates precise one-to-one equivalences to other resources and validates them with OWL reasoning, so a MONDO ID can be translated to an Orphanet or OMIM code with confidence. Each disease also carries synonyms and its place in the hierarchy, from broad groupings down to specific subtypes.
Mondo is open, licensed under CC BY 4.0, and released every month.
Mondo is free to browse, search and download.
EMBL-EBI's Ontology Lookup Service (OLS) hosts the current Mondo release. Search a disease name to get its MONDO ID, definition, synonyms and cross-references.
From a disease, move up to its parent groupings or down to its subtypes. This is how you see that "lung cancer" includes lung carcinoma, and below it non-small cell and small cell lung carcinoma.
Use the cross-references and equivalences on each record to move between MONDO and codes such as OMIM, Orphanet or NCIt.
Each monthly release on the Mondo GitHub repository is published in OBO, OWL and JSON, including a base edition and other variants, for loading into your own tools.
To use Mondo on trial or patient data, map each free-text condition to a MONDO ID, then query by ID and include descendants to capture subtypes.
ClinicaLister maps the conditions on ClinicalTrials.gov records to MONDO diseases — more than 500,000 trials so far — using exact matching on names and synonyms plus AI-assisted mapping for the long tail.
Search by disease and ClinicaLister includes trials registered under any synonym or subtype, so "lung cancer" also returns NSCLC and SCLC trials without listing every name by hand.
Each disease leads to its trials and the molecules being tested for it, giving a competitive landscape built on a shared definition rather than keyword overlap.
Through the ClinicaLister MCP server, Claude and other assistants resolve a disease to its MONDO ID first, then pull every matching trial and molecule.
36,000+
MONDO concepts held (full release)
500,000+
trials mapped to MONDO diseases
~84%
of trials that list a condition are mapped
Weekly
check for new Mondo releases
ClinicaLister loads the full Mondo release with its synonyms. Trial mapping coverage keeps growing across the long tail of rare and loosely worded conditions. Counts as of August–September 2026.
Mondo is an open disease ontology from the Monarch Initiative that merges many disease vocabularies — OMIM, Orphanet, the Disease Ontology, NCIt, ICD and others — into one hierarchy with a stable MONDO ID per disease.
Monthly. Each release is published on the Mondo GitHub repository in OBO, OWL and JSON formats.
Yes. Mondo is licensed under CC BY 4.0, which allows reuse with attribution.
Search the disease name in EMBL-EBI's Ontology Lookup Service or on the Mondo website. For example, lung cancer is MONDO:0008903.
Mondo merges those resources rather than replacing them. Each MONDO disease carries cross-references to the matching OMIM, Orphanet, ICD, NCIt or other codes, and Mondo curates precise one-to-one equivalences where the concepts truly match.
Sponsors describe the same condition in many ways. Mapping each trial to a MONDO ID lets one search find every trial for a disease and its subtypes, which keyword search misses.
Search trials by disease, subtypes included
Built for the Clinical Researcher / Scientist. See it in the product: Diseases & Knowledge Graph. All data sources