Subcutaneous injection of normal allogeneic kidney and liver tissues extended survival of DBA/2Cr mice challenged with a lethal dose of syngeneic L5178Y lymphoma cells. Immunization with a combination of tissues from five strains provided far more protection than immunization with tissue from any single strain. It is suggested that the basis of this protective effect is a cross-reactivity or identity between tumor-associated transplantation antigens (TATA) on the L5178Y tumor and non-H-2 alloantigens normally expressed by some allogeneic tissues.