The subcellular distribution of the tumor-associated transplantation antigens (TATAs) of two highly immunogenic methylcholanthrene-induced sarcomas, Meth A and CI-4, were compared. Most of the TATA of CI-4 was found in the soluble fraction (cytosol) of the cell while the TATA from Meth A was variably distributed between the membrane and cytosol. The soluble fraction TATAs from both tumors were very immunogenic and their strong immunity could not be influenced by administering antigen in a variety of protocols that altered the immune response in other systems. The soluble fraction and membrane-associated TATAs from both tumors could be specifically bound to liposomes in reconstitution experiments and the antigenicity of all of the TATAs was significantly enhanced when they were incorporated into these artificial membranes.