The ChEMBL database, an open large-scale bioactivity database, has been updated with new data sources and improvements in functionality. Key enhancements include comprehensive tracking of compounds from research stages through clinical development to market, a new richer data model for representing drug targets, and methods to help users identify reliable data. The database now includes data from United States Adopted Name applications, allowing for more detailed tracking of compounds in development. A new target data model distinguishes between targets and molecular components, providing clearer information on protein complexes and subunits. Additionally, the database offers physicochemical properties, ligand efficiencies, and standardized activity types to help users assess data quality and compare bioactivity values. The ChEMBL interface has been improved with enhanced search capabilities, report cards, and cross-references to other resources. Data can be accessed via a web interface, downloads, and web services, including an RDF format for semantic web integration.The ChEMBL database, an open large-scale bioactivity database, has been updated with new data sources and improvements in functionality. Key enhancements include comprehensive tracking of compounds from research stages through clinical development to market, a new richer data model for representing drug targets, and methods to help users identify reliable data. The database now includes data from United States Adopted Name applications, allowing for more detailed tracking of compounds in development. A new target data model distinguishes between targets and molecular components, providing clearer information on protein complexes and subunits. Additionally, the database offers physicochemical properties, ligand efficiencies, and standardized activity types to help users assess data quality and compare bioactivity values. The ChEMBL interface has been improved with enhanced search capabilities, report cards, and cross-references to other resources. Data can be accessed via a web interface, downloads, and web services, including an RDF format for semantic web integration.