Seventy-one patients with metastatic colorectal carcinoma(CRC) were treated with varying doses of the mouse monoclonal antibody (MAb) 17-1A. One patient achieved a partial remission (PR) (1%) with a survival duration of 114+ months. Further 10 patients showed a minor response (MR) or stable disease > 3 months (SD) (14%). In patients receiving a total dose of MAb17-1A < 2 g the overall response rate was 22% (10/45) (1 PR, 2 MR, 7 SD) while patients treated with a total dose > 2 g had a corresponding figure of 4% (1/26) (1 MR) (p < 0.05). Responding patients (n = 11) survived significantly longer than non-responding patients (n = 60) (median: 20 vs 10 months) (p < 0.0027). In the most intensive treatment group (total 12 g), 14 patients received 500 mg of MAb17-1A tiw for 8 weeks. The frequency and intensity of side-effects were mild and did not cause withdrawal or dose reduction of MAb17-1A, even in the 12 g dose schedule. Patients with a pretreatment ADCC (antibody dependent cellular cytotoxicity) activity above the median of all patients, survived significantly longer than those with a low value (p < 0.05).