The chemosensitivity test should be performed to individualize the chemotherapy for patients with gastrointestinal cancer, which is one of the tumors most refractory to treatment by anticancer drugs. The present study was designed to determine the chemosensitivity in fresh human gastrointestinal cancer, using highly purified tumor cells, and the correlation of this sensitivity with clinical response. The clinical responses were obtained in 15 of the 25 patients, and 5 of the 15 patients with gastric cancer and colorectal cancer, respectively. The inhibition rates for anticancer drugs in responders were higher than in nonresponders. Thus, it is suggested that the chemotherapy according to the results of the MTT assay is effective in patients with gastrointestinal cancer.