BALB/c-nu mice were injected with 10(6) normal congenic thymocytes. This number of cells permits only partial reconstitution and in individual mice some functions were restored and others were not. The relationships between the functions of skin graft rejection, circulating alloantibody production and the ability to generate, in vitro, cytotoxic T cells were studied with regard to the strains CBA and C57BL/6.