Two unresectable advanced gastric cancer cases with peritoneal metastases were successfully treated by the combination therapy of S-1 and paclitaxel. S-1 (1.25m(2): 80 mg/day, 1.25m(2)-1.50m(2)<:120 mg/day) was administered orally for 14 consecutive days followed by 14 days rest and a 2-hour infusion of paclitaxel (50 mg/m(2)) was administered on day 1 and 15 of each course. Treatment was repeated every 4 weeks unless disease progression or severe adverse effects were observed. Case 1: 65-year-old male (performance status: PS 3) with type 1 gastric cancer with malignant ascites. Case 2: 66-year-old male (PS3) with peritoneal metastases whose primary gastric lesion was surgically resected. Partial response was obtained in the former and complete response in the latter. Combination therapy of S-1 and paclitaxel can be highly recommended for patients with inoperable gastric cancer with poor PS.