Summary o 1.The natural history of skin homografts in dogs resembles closely that already observed in rabbits. 2.A dog previously sensitised with skin will immediately react against a kidney homotransplanted from the same dog which provided the skin. 3.Skin homografts on a dog which has previously been sensitised with a homotransplanted kidney will not survive for as long as skin homografts normally do. 4.It is concluded that kidney and skin of the dog share important antigens and that the immunity evoked by homologous tissue is individual and not tissue-specific.