The Tumor Gene Family Databases (TGDBs) contain a broad range of data about the genes involved in cancer (e.g. proto-oncogenes and tumor supressor genes). At present, there are two component databases in addition to TGDB itself, the Oral Cancer Gene Database (OrCGDB) and the Breast Cancer Gene Database (BCGD). The component databases provide information which is more relevant to a specific disease (e.g. which subset of genes are involved in breast or oral cancer) and have different editorial policies (e.g. facts entered into BCGD and OrCGDB are reviewed by independent editorial boards before being made public whereas TGDB is reviewed only by its curators). On the other hand, data can be readily shared between component databases where appropriate. Gene data includes mechanisms of oncogenic activation, regulation, frequency of involvement in various tumor types, and chromosomal location. Data about the encoded proteins includes the cell type in which they are found, subcellular location, DNA, protein, and ligand binding, role in development, and normal biochemical function. The data in the TGDBs are extracted from the literature, organized by topic, structured into discrete facts, and linked to other resources such as PubMed, GeneCards, and On-Line Mendelian Inheritance in Man. The TGDBs can be searched by text words or by gene name, the latter facilitated by an extensive list of gene name synonyms. Because data entry as well as data retrieval is accomplished via the World Wide Web, TGDB has been used as an international collaborative resource.