The objectives of this contract are to provide a small animal facility capable of (1) maintaining a colony of mice, rabbits, rats and hamsters to support ongoing research in the areas of transplantation, cancer biology and diagnosis, and immunology. The research includes the study of the role of H-2 and T cell receptor products in the immune response of well-defined mouse strains to tumors and transplantation antigens; (2) breeding special congenic strains of mice not available commercially; (3) providing a technical staff capable of performing bleedings and injections of mice and rabbits, skin grafting of mice, injections and harvesting of mouse ascites tumors, and palpation of mice for detection of tumors; (4) maintaining a freezer bank of serologic products to be used in conjunction with these animals; and (5) cryopreservation of fertilized embryos for future retrieval of individual strains of mice. All animals will be supplied by the Government.