Sequential methotrexate (MTX) and 5-FU plus leucovorin and mitomycin (MMC) was given to 52 patients with disseminated, measurable colorectal cancer. Complete and partial responses were seen in 19 of 49 (39%) evaluable patients. Nine additional patients achieved a minimal response. Median overall survival was 8.8 months, while that for patients objectively responding was 13.6 months. This study utilized a MTX exposure period of 12 hours prior to 5-FU. In comparison to other trials utilizing sequential MTX and 5-FU, the addition of MMC to the regimen may improve the response rate but increases the incidence of adverse effects, particularly myelosuppression and renal toxicity. This phase II trial suggests that sequential MTX and 5-FU plus leucovorin and MMC is an active combination therapy and warrants further comparative trial in patients with large bowel cancer.