A phase 11 trial of citrovorum factor, 500 mg/m2/week, plus 5-fluorouracil, 400 mg/m2/week on day 1, and cisplatin, 20 mglm2lweek on day 2, was carried out in a group of 40 patients with metastatic colorectal carcinoma. A partial response with a mean duration of 8.4+ months was achieved in 24% of patients, a minimal response with a mean duration of 5.4 months was obtained in 6% of patients, and a stabilization of 6.2 months was achieved in 41%. Ten patients (29%) progressed. A 38% partial response rate was seen in patients with advanced rectal carcinoma, whereas no response was obtained in patients with colon cancer. Interestingly, 5 partial responses were seen in 12 patients pretreated with 5-fluorouracil. The overall survival was 9.8+ months. The mean survival of patients who achieved a partial response was 12.0+ months, whereas patients who progressed survived a mean of 6.6+ months. Patients with colon cancer had a mean survival of 8.1 + months, and those with rectal cancer survived a mean of 11A + months. This difference was not statistically significant. The treatment was generally very well tolerated, with patients showing mostly grade 1-2 gastrointestinal and Ior hematological toxicity.