The KEGG database project was initiated in 1995, originally as part of the Japanese Human Genome Program (4). Since then we have been organizing our knowledge of cellular functions and organism behaviors in computable forms, especially in the forms of molecular networks (KEGG pathway maps) and hierarchical lists (BRITE functional hierarchies). This computerized knowledge has been widely used as a reference for biological interpretation of large-scale datasets generated by sequencing and other high-throughput experimental technologies. Our efforts are now focused on human diseases and drugs. We consider diseases as perturbed states of the molecular system that operates the cell and the organism, and drugs as perturbants to the molecular system. There are a number of disease databases available (5), but they are mostly descriptive databases for humans to read and understand. In KEGG, disease information is being organized in more computable forms: pathway maps and gene/molecule lists. Here, we summarize the current status of the KEGG project and the new developments of the KEGG DISEASE and KEGG DRUG databases that comprise KEGG MEDICUS.
