Between January 1986 and August 1991, 19 patients with alimentary tract cancers complicated by peritoneal dissemination received whole abdominal irradiation combined with intraperitoneal chemotherapy postoperatively. Using a moving-strip technique of irradiation, 12.0 Gy was delivered in three fractions to the entire abdominal contents with partial liver and kidney shielding. The primary tumor sites were the stomach in 12 patients, the colorectum in five, and the gall bladder in two. Nine patients with gross residual disease also received a limited field boost of 30.6 Gy in 17 fractions after completion of treatment to the whole abdomen. None of the patients failed to complete the planned dose despite acute gastrointestinal toxicity (nausea and vomiting, 84%, diarrhea and cramping, 78%) and acute hematologic toxicity (leukocytopenia, 84%, thrombocytopenia, 68%). Our follow-up study revealed that the actuarial one-year survival rate was 28.4% and the median survival time was 9.0 months. Survival rates at one-year for patients with colorectal and gastric cancer were 75.0% and 16.7%, respectively. Patients with gastric cancer (n = 12) had a poorer outcome than those with colorectal cancer (n = 5) in the present study. One reason for this difference may have been the presence of cancerous pleuritis, which was frequently observed in patients with gastric cancer. Therefore, more intensive treatment to prevent cancerous pleuritis seems to be necessary to improve the efficacy of whole abdominal irradiation.