Forty four patients who had documented progression of metastatic colorectal cancer while receiving 5-fluorouracil (5-FU) monotherapy were treated with continuous infusion 5-FU, 300 mg/mg2/day, plus weekly low-dose cisplatin, 20 mg/m2. Treatment was given in 12-week cycles, consisting of 8 weeks of chemotherapy followed by a 4-week rest period, and was well tolerated. Three of 23 patients (13%) who had failed bolus 5-FU but not been exposed previously to infusional 5-FU responded. Of 21 patients who had failed infusional 55-FU monotherapy, only one (5%) responded. Time to progression (5.7 vs. 1.8 months) and survival (12 vs. 5.5 months) were significantly longer for patients who had not previously received infusional 5-FU but who had failed bolus schedules, compared with patients who had previously failed infusional 5-FU (p less than .001).