The sequential intraperitoneal injection of five different A strain tumors into DBA/2 mice resulted in the de novo generation of new DBA/2 tumors. These new tumors share many identical characteristics including the expression of surface H2d, FcR, LY6.2 and tumor antigens. All have the same karyotype which differs in number and in the presence of two metacentric chromosomes from the original A strain tumors. Phenotypically, all are vigorously metastatic after intraperitoneal, subcutaneous, intradermal or intravenous injection. None of the original A strain tumors are metastatic in the A strain host. These tumors have thus provided us with a good model for the study of metastasis while raising questions regarding the oncogenicity of tumors.