The world-renowned Mouse Mutant Stocks Center at the Jackson Laboratory in Bar Harbor, Maine, has two important functions: (1) research on new mutants of the mouse; and (2) maintenance and distribution of mouse mutants and genetic information about them to the scientific community. Mutants that have potential value for biomedical research are maintained in the colony with constant genetic backgrounds and, when necessary, by special genetic techniques. Mutants with controls or breeding pairs of mutation carriers are distributed to scientists world wide upon request. The Center also assembles information on mouse genes and provides other scientists with comprehensive linkage maps of the mouse, a computer list of genes with information about them, and a computerized strain-by-locus matrix of polymorphic loci. This award provides a partial subsidy for the maintenance and distribution functions of the Mouse Mutants Stock Center.