ATLAS is an open-source software tool developed by OHDSI (Observational Health Data Sciences and Informatics) to support the design and execution of analyses on standardized, patient-level clinical data. It enables researchers to explore clinical data, define cohorts, and characterize populations using the OMOP Common Data Model.
Build and refine complex cohort definitions using clinical concepts, inclusion/exclusion criteria, and temporal logic across the OMOP CDM.
Characterize patient populations with summary statistics on demographics, conditions, drugs, procedures, and more — without accessing individual records.
Browse and search the OMOP vocabulary to identify the right clinical concepts, code sets, and hierarchies for your research question.
Rapidly assess cohort feasibility and estimate achievable sample sizes before committing to a full study design or IRB submission.