Advanced intra-abdominal cancers are frequently associated with malignant ascites. The aim of this study was to document the frequency and clinical course of patients found to have large-volume ( > or = 3 L) malignant ascites when undergoing a major abdominal operation. Between October 1, 1987 and September 1, 1992, 385 patients with malignant ascites were admitted to hospitals associated with a university medical center. Seventeen with large volume ascites underwent exploration for palliation of bowel obstruction or debulking of tumor. Operative mortality was 41% and mortality correlated with the presence of a nonovarian primary and advanced age. We conclude that patients with large volume nonovarian malignant ascites have a high mortality rate following a major abdominal operation. New approaches such as neoadjuvant or intraperitoneal chemotherapy or possibly peritoneovenous shunt placement at the time of the abdominal operation, are needed to improve the dismal results in this subgroup of patients.