BioGRID is a freely accessible database of physical and genetic interactions, available at http://www.thebiogrid.org. It contains over 116,000 interactions from Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and Homo sapiens. Version 2.0 includes over 30,000 interactions from 5778 sources, curated from the primary literature. The database provides a web interface for searching and retrieving interaction data, and allows users to download datasets in tab-delimited text files and PSI-MI XML. Pre-computed graphical layouts of interactions are available in various formats, and users can construct customized graphs with embedded protein, gene, and interaction attributes using the Osprey visualization system. BioGRID was originally developed as a laboratory information management system for high-throughput (HTP) interaction data. It now includes HTP interaction data from multiple species, including yeast, nematode, fruit fly, and human. The database also contains literature-derived interactions, including 19,744 protein interactions and 11,234 genetic interactions from the primary literature. In addition, BioGRID includes imports of 10,943 literature-derived genetic interactions from Flybase and 30,761 literature-derived interactions from HPRD, totaling over 70,000 literature interactions. The BioGRID web interface is supported by PHP and MySQL, and allows users to search using gene names, ORF names, PubMed IDs, and free text. The interface compiles interaction redundancies and provides annotation-rich results. BioGRID is also linked to other databases such as the Saccharomyces Genome Database, Flybase, and Germ Online. BioGRID supports data exchange standards such as PSI version 2.5, and provides downloadable files in multiple formats. The database is freely available for download and can be hosted on in-house servers. Future developments include curating interactions from major model organisms, supporting quantitative genetic interactions, and enabling cross-species predictions through BLAST-based alignments. A planned open source release, ProtoGRID, will simplify installation of local versions of BioGRID. The database is actively maintained and updated, with new data added regularly.BioGRID is a freely accessible database of physical and genetic interactions, available at http://www.thebiogrid.org. It contains over 116,000 interactions from Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and Homo sapiens. Version 2.0 includes over 30,000 interactions from 5778 sources, curated from the primary literature. The database provides a web interface for searching and retrieving interaction data, and allows users to download datasets in tab-delimited text files and PSI-MI XML. Pre-computed graphical layouts of interactions are available in various formats, and users can construct customized graphs with embedded protein, gene, and interaction attributes using the Osprey visualization system. BioGRID was originally developed as a laboratory information management system for high-throughput (HTP) interaction data. It now includes HTP interaction data from multiple species, including yeast, nematode, fruit fly, and human. The database also contains literature-derived interactions, including 19,744 protein interactions and 11,234 genetic interactions from the primary literature. In addition, BioGRID includes imports of 10,943 literature-derived genetic interactions from Flybase and 30,761 literature-derived interactions from HPRD, totaling over 70,000 literature interactions. The BioGRID web interface is supported by PHP and MySQL, and allows users to search using gene names, ORF names, PubMed IDs, and free text. The interface compiles interaction redundancies and provides annotation-rich results. BioGRID is also linked to other databases such as the Saccharomyces Genome Database, Flybase, and Germ Online. BioGRID supports data exchange standards such as PSI version 2.5, and provides downloadable files in multiple formats. The database is freely available for download and can be hosted on in-house servers. Future developments include curating interactions from major model organisms, supporting quantitative genetic interactions, and enabling cross-species predictions through BLAST-based alignments. A planned open source release, ProtoGRID, will simplify installation of local versions of BioGRID. The database is actively maintained and updated, with new data added regularly.