Ten patients with metastatic colorectal carcinoma were treated with MAb 17-1A (IgG2A). Before infusion, MAb was incubated in vitro with isolated autologous blood mononuclear cells. Treatment was given in repeated courses (2-4 times) to a maximum dose of 1000 mg of MAb 17-1A. One patient achieved a clinical complete remission, two patients had a minor response and one patient had stable disease for 5 months. The median survival for the four responders was 19 months compared to 7 months for the six non-responders. Therapy was well tolerated. In this series, 32 infusions of MAb 17-1A were given. The serum half-life of MAb 17-1A was approximately 22 hours. All patients developed anti-mouse antibodies of both IgG and IgM classes. No relation between adverse reactions and anti-mouse antibodies was seen. At 3 occasions allergic reactions were noted. Skin test with MAb 17-1A seems to reliably predict for allergic reactions.