An in vitro chemosensitivity study of both biopsy specimens and surgically resected tumors of advanced gastric cancer from 12 patients was evaluated using the succinate dehydrogenase inhibition (SDI) test. A decrease in succinate dehydrogenase (SD) activity as an indicator of chemosensitivity was determined using cisplatin (CDDP), etoposide (VP-16), and mitomycin C (MMC). In this study, 29 of a total 36 experiments were evaluable (80.6%) and significant correlations were found in all three of the antitumor drugs (P < 0.03). This finding suggests that the SDI test using biopsy specimens may prove valuable for assessing the preoperative chemosensitivity of advanced gastric cancer.