The Mouse Tumor Biology (MTB) Database supports the use of the mouse as a model system of hereditary cancer by providing electronic access to Information on endogenous spontaneous and induced tumors in mice, including tumor frequency & latency data, information on genetically defined mice (inbred, hybrid, mutant, and genetically engineered strains of mice) in which tumors arise, and information on genetic factors associated with tumor susceptibility in mice and somatic genetic-mutations observed in the tumors.