i2b2 – Informatics for Integrating Biology and the Bedside (i2b2) is an NIH-funded National Center for Biomedical Computing based at Partners HealthCare System. i2b2 has been released as a collection of open source software tools that facilitate the collection and aggregation of patient data, both clinical and research, into a translational research repository. The basic function of the software is to allow the user to identify cohorts of patients from a large repository of observations. The core code manages projects, files, query ontology, data and workflows. It is designed to allow developers to add functional modules to the core code. These include ETL procedures to move data from a commercial EHR to the repository; web-based forms allowing direct data entry; reporting and visualization tools; file uploading and validation capabilities through range checks and logic rules; robust audit trails; data exporting tools; search repositories for cohorts of patients meeting criteria for clinical research studies.