Several studies have tried to improve the surgical results after resection for gastric cancer by different adjuvant therapy protocols, including intraoperative radiotherapy (IORT). Since 1990 we have performed a randomized, prospective trial comparing surgery alone and surgery plus adjuvant IORT to evaluate the role of adjuvant intraoperative radiotherapy in the treatment of curative resected gastric carcinomas. In the present study, p53, bcl-2 immunoreactivity and DNA fragmentation as a typical marker of apoptosis were determined to investigate the predictive value of apoptosis-related factors and the observed response to radiotherapy. Preliminary data indicate that patients with tumors containing increased numbers of apoptotic tumor cells might derive benefit from adjuvant IORT.