Nineteen patients with metastatic adenocarcinoma of the colon or rectum were treated with alpha (human leukocyte) interferon (alpha IFN). Patients received 3 X 10(6) IU/day of interferon im 5 days/week. Eighteen patients are evaluable for response and toxicity. There were no objective responses. All evaluable patients demonstrated progression of disease during therapy. Toxicity consisted primarily of mild granulocytopenia, thrombocytopenia, fatigue, weakness, and fever. This trial demonstrates that while alpha IFN can be administered safely as scheduled, this regimen has no activity against adenocarcinoma of the colon/rectum.