OBJECTIVE: To determine the dose-limiting toxicity (DLT) and the maximum-tolerated dose (MTD) of combination chemotherapy with leucovorin-modulated weekly bolus 5-fluorouracil (5-FU) and weekly paclitaxel in patients with advanced gastric cancer (GC). METHODS: Chemotherapy-naive patients with histologically proven metastatic or recurrent GC were enrolled. Paclitaxel was administered as a 1-h intravenous (i.v.) infusion followed by 5-FU as a bolus i.v. infusion on Days 1, 8 and 15. A 2-h i.v. infusion of l-leucovorin was started at the same time as the paclitaxel infusion on Days 1, 8 and 15. Treatment cycles were repeated every 28 days until disease progression or unacceptable toxicity occurred. Patients were scheduled to receive 5-FU, l-leucovorin and paclitaxel at four dose levels (mg/m(2)/week): 500/250/60 (level 1), 500/250/80 (level 2), 600/250/80 (level 3) and 600/250/100 (level 4), respectively. RESULTS: Eighteen patients were enrolled. During the first cycle of the highest dose level (level 4), two of the six patients had DLT involving Grade 3 diarrhea and Grade 3 skin rash. Furthermore, three of the four patients who received the second consecutive cycle of treatment at dose level 4 had Grade 4 neutropenia. Dose level 3 was thus determined to be the MTD. Eleven (61%) of the 18 patients had partial responses, and the median progression-free survival time was 6.8 months. CONCLUSIONS: The MTD and the recommended dose for phase II studies of this regimen were determined to be 5-FU 600 mg/m(2)/week, l-leucovorin 250 mg/m(2)/week and paclitaxel 80 mg/m(2)/week.