Our previous experience has demonstrated that growth of gastric cancer during the waiting period for surgery cannot be neglected, and some patients hope to receive prophylactic treatment to inhibit the growth of tumor until surgery. The present study was designed to assess the clinical benefits of preoperative chemotherapy with oral UFT for gastric cancer during the waiting period for surgery. Fifty patients with gastric cancer (24 early, 25 advanced and 1 recurrent cancers) were treated with oral UFT at 300-600 mg/day for 7-36 days before surgery and the objective responses and the postsurgical survivals were evaluated. In 42 of 50 patients objective responses of primary lesions were assessed by endoscopy or upper gastrointestinal series examination, and 2 CRs, 15 PRs and 25 NCs were seen (40% response). The histological effect was evaluated in 50 patients and the following classifications were made: grade 3 (complete disappearance or necrosis of tumor cells), 2; grade 2 (necrotic changes > 2/3 area), 4; grade 1b (> 1/3 area), 7; grade 1a (< 1/3 area), 15; and grade 0 (no histological changes), 22. A longer period of UFT administration was associated with CR or PR. All the patients underwent gastrectomy (38 curative and 12 palliative gastrectomies): all patients with Stage I-III primary gastric cancer are alive after surgery, and the 50% survival period of the patients with Stage IV cancer was 20 months. The side effects were not serious, including slight myelotoxicity, liver dysfunction and anorexia. It is concluded that preoperative chemotherapy for gastric cancer with oral UFT on outpatient basis may result in down-staging as well as the prevention of tumor growth during the waiting period for surgery without serious side effects.