Locoregional administration using OK-432 was evaluated in treating malignant effusion. Positive clinical responses were seen in 19 (52%) of 36 gastric cancer patients, and in 9 (90%) of 10 colon cancer patients (p < 0.05), indicating its clinical benefit in treating malignant effusion of colon cancer. Fever elevation was observed in 43 (93%) patients and local pain occurred with 9 (20%) of 46 administrations. Immunological analysis for responder patients with rectal cancer revealed that OK-432 induced autologous tumor-reactive CD 3+ CD 4+ TCRV beta 20+ killer lymphocytes. The TCR gene analysis permitted us to clone a V beta 20 CDR 3 sequence, by which positive bands were shown in 3 (75%) of 4 responders and negative bands in 3 (100%) of 3 non-responders. It is suggested that cross-antigenicity exists between OK-432 and colon cancer, and that genetic analysis using the TCRCDR 3 sequence makes it possible to predict responder patients to OK-432 immunotherapy.