BACKGROUND: Published data suggests that docetaxel combined with 5-fluorouracil (5-FU) may have synergistic activity in treating advanced gastric cancer. We performed a phase I study of docetaxel and 5-FU to determine the maximum tolerated dose (MTD), the recommended dose for phase II studies, and the safety of this combination. METHODS: Eligible patients had recurrent and/or metastatic advanced gastric cancer with normal cardiac, renal and hepatic function. Traditional phase I methodology was employed in assessing dose-limiting toxicity (DLT) and MTD. On day 1 every 3 weeks, docetaxel 75 mg/m2 (fixed dose) was infused over 1-h, followed immediately by 5-FU as a 5-day continuous infusion. RESULTS: Dose escalation schema was as follows: dose level (DL) 1 (5-FU 250 mg/m2/day), 2 (500), 3 (750), and 4 (1000). Three patients were enrolled on DL1, without DLT. On DL2, 1 DLT (grade 3 stomatitis) was developed in first 3 patients, and this cohort was expanded to 6 patients. Three patients had been enrolled on DL3. Because two out of 3 patients had DLTs, the MTD was reached at DL3. CONCLUSION: The recommended phase II dose of this combination is 75 mg/m2 docetaxel on day 1 immediately followed by a 5-day continuous infusion of 5-FU 500 mg/m2/day.