Two cases of advanced adenocarcinoma treated with attenuated vaccinia virus AS strain are reported. One was a primary lung adenocarcinoma with metastatic lesions in brain, right kidney, and rib. The other was a left renal adenocarcinoma with multiple lung and vertebral metastases. In both patients, good antitumor effects against lung and bone lesions were obtained, respectively, and no adverse reactions were noted. Therefore, treatment of patients with AS vaccinia virus appears to suppress the growth of tumor cells without adverse effects on normal human cells. This is the first report to describe the effects of attenuated vaccinia virus AS strain on human cancer.