This phase I trial evaluated the combination of oxaliplatin plus UFT in patients with advanced solid tumors to determine the maximum tolerated dose (MTD) and the dose limiting-toxicity for future phase II trials. Eligible patients (N = 27) were treated in sequential cohorts of three to six patients. The starting doses for oxaliplatin and UFT were 70 mg/m2 and 250 mg/m2/day respectively, and five dose levels were designed up to 85 mg/m2 and 400 mg/m2/day. Oxaliplatin was administered i.v. on day 1 and 15, and oral UFT was given daily in three divided doses on days 1-21 followed by 1 week rest of a 28-day cycle. At the recommended dose, six additional patients were entered. In total, 79 courses were administered with a median of 3 (range 1-6). MTD was not reached; oxaliplatin 85 mg/m2 on day 1 and 15 plus UFT 400 mg/m2/day for 21 days was considered the optimum combination for phase II trials. Gastrointestinal toxicity and asthenia were the most common adverse events. Eight out of 13 patients (61.5%) with metastatic colorectal cancer achieved stable disease. UFT plus oxaliplatin is a feasible and safe combination. A phase II trial in first-line advanced colorectal cancer is ongoing.