We studied the therapeutic effect of OK-432 combined with adoptive immunotherapy in 19 cases of liver metastases from breast cancer. Of the 14 patients who received intraarterial OK-432 injection and transfer of cultured lymphocytes, 9 responded to this therapy, whereas no patients responded to intravenous administration. The minimum cell number for a therapeutic response was 8 x 10(8) cells. Metastatic lesions other than those in the liver regressed after therapy in 4 patients. The serum carcinoembryonic antigen level paralleled the therapeutic effect. There were no severe side-effects accompanying this therapy. These results indicate that intraarterial adoptive immunotherapy combined with OK-432 is effective as a new therapeutic approach against liver metastases from breast cancer.