The Japanese Society of Hyperthermia conducted a multicenter trial to study the effect of thermochemotherapy for gastrointestinal cancer. Ninety patients, including 33 patients with gastric cancer, 30 patients with large bowel cancer and 27 patients with pancreatic cancer, received thermochemotherapy. The effects on shrinkage of tumor size, life span, performance status and quality of life were ... [Show full abstract] compared with the results of matched patients who received chemotherapy alone. Auti-tumor response was observed in 45 %, 16 % and 30% of patients with gastric, large bowel and pancreatic cancer by thermochemotherapy, respectively. These figures in the chemotherapy groups were 23 %, 7% and 7% (p < 0.04 between the thermochemotherapy and chemotherapy groups in gastric cancer and pancreatic cancer). In the thermochemotherapy group, 50% of patients survived for 6, 10 and 7 months in gastric, large bowel and pancreatic cancer, respectively. In the chemotherapy group, these figures were 5, 5 and 2 months (P < 0.0001 between the two groups in large bowel cancer and pancreatic cancer). Performance status was improved in 44 %, and cancer pain was relieved in 75 % of patients received thermochemotherapy. There was no serious side effect in hyperthermia treatment, and thermochemotherapy was well-tolerable by patients. Thus, thermochemotherapy is a powerful tool for cancer treatment by exerting not only anti-tumor effects but also improvement in performance status, cancer pain and quality of life.