Syngeneic tumour transplants to inbred female animal strains were carried out with basaliomas, squamous cell carcinomas and fibrosarcomas of the skin, induced by DMBA (9,10-dimethyl-1,2-benzanthracene) in the mouse, rat and guinea pig. A completely successful transplantation of all tumors was only achieved in the group of fibrosarcomas of the rat when a myocardial suspension of a young rat was used as a "supporting agent". This may be a new immuno-biological aspect in tumor transplantation. In the other groups, five tumors developed in the host animals after a period of latency of 10 months or more. Therefore, it is discussed whether two of these tumors grown in the host rats should be considered spontaneous. In addition I have found no earlier reports in the literature with successful DMBA-induced epidermal tumors transplantations in homologous or syngeneic animal strains. Tumors were grafted on to altogether 100 animals.