We retrospectively evaluated the clinical usefulness of the succinate dehydrogenase inhibition (SDI) test as a chemosensitivity test, using 168 resected specimens of gastric cancer, with special reference to the correlation between the results of the SDI test and clinical effects of the corresponding chemotherapy. The rate of sensitivity of these tissues to DDP, CQ, ACR, MMC, ADM, and 5-FU were 63.59'0, 54.29'0, 47.4%, 42.9%,, 3 1.4%, and 10.8%, respectively. Survival rates for patients with a positive chemosensitivity to MMC and postoperatively prescribed more than 20 mg of MMC were significantly better than those without sensitivity to MMC, even when treated with MMC, although no statistical differences existed in clinicopathologic factors between the two groups. We conclude that the SDI test for human gastric cancer is a rapid, reliable. and useful assay to determine the compatibility between the results of assay and the clinical effects of corresponding chemotherapy. We propose that the regimen of postoperative adjuvant chemotherapy be tailored according to results of the SDI test, using tissues resected from individual patients. Q 1994 WiIey-Liss. Inc.