Peritoneal carcinomatosis from appendical or colorectal cancer has been regarded as a fatal clinical entity. We used cytoreductive surgery and intraperitoneal chemotherapy to treat consecutive patients with peritoneal carcinomatosis. There were 43 colorectal and 104 appendiceal cancer patients. The mean follow-up was 32 months, with a range of 0-140 months. Clinical features that showed prognostic significance included appendiceal versus colorectal primary (p < 0.0001), grade I versus grades II and III histopathology (p < 0.0001), complete versus incomplete cytoreduction (p < 0.0001), lymph node-negative versus lymph node-positive primary tumor (p < 0.0001), volume of peritoneal carcinomatosis present preoperatively for colon cancer (p < 0.0002), and nonmoderate versus heavy prior surgery (p < 0.0043). Features with no statistical prognostic significance include tumor volume for appendiceal cancer, age, sex, number of cycles of chemotherapy, operative time, complications, blood loss, and institution providing treatment. From these prognostic features, four staging groups were identified and 5 year survival was estimated by the product-limit survival method. Group I patients (n = 61) were those with grade I histology, no lymph node metastases, and a complete cytoreduction (survival at 5 years = 90%). Group II (n = 20) patients are those with grade II or III histology, no lymph node metastases, and a complete cytoreduction (62%). Group III patients (n = 22) had any histology, lymph node metastases, and a complete cytoreduction (45%). Group IV patients (n = 44) had an incomplete cytoreduction (12%). Peritoneal carcinomatosis is a treatable condition in selected patients with a possibility for long-term disease-free survival.