Caffeine, which has a DNA-repair inhibiting effect, enhances the cytocidal effects of anticancer drugs and radiation. We present a preliminary report on the results of a new treatment, "radiochemotherapy combined with caffeine" (K3 protocol), for high-grade soft tissue sarcomas. Seventeen patients with various high-grade soft tissue sarcomas were included in this study. Preoperatively, three to five courses of intra-arterial chemotherapy using cisplatin, caffeine and doxorubicin after radiation therapy were administered. Following the preoperative therapy, function-saving surgery was performed for all cases. Complete response was observed in six patients, partial response in six and no change in five. The effectiveness rate of caffeine-potentiated radiochemotherapy was therefore 71%. The histological response for radiochemotherapy was better than that for chemotherapy alone, that is, total tumor necrosis was identified in six patients and over 90% necrosis in another six. Complications resulting from the preoperative radiation comprised of serious inflammation in three patients and skin necrosis in another three. Twelve patients have remained free of disease, two patients are alive with disease and three have died of metastatic disease with a mean follow-up period of 36 months. There was no local tumor recurrence. These preliminary findings suggest that caffeine-potentiated radiochemotherapy contributed to a satisfactory local response and the success of function-saving surgery for high-grade soft tissue sarcomas.