This paper presents current progress in the development of semantic data integration environment which is a part of the Biomedical Informatics Research Network (BIRN; http://www.nbirn.net) project. BIRN is sponsored by the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH). A goal is the development of a cyberinfrastructure for biomedical research that support advance data acquisition, data storage, data management, data integration, data mining, data visualization and other computing and information processing services over the Internet. Each participating institution maintains storage of their experimental or computationally derived data. Mediator based data integration system performs semantic integration over the databases to enable researchers to perform analyses based on larger and broader datasets than would be available from any single institution’s data. This paper describes resent revision of the system architecture, implementation, and capabilities of the semantically based data integration environment for BIRN.