OUTLINE: This is a randomized, multicenter study. Patients are stratified according to center, risk group, presence of symptoms (yes vs no), and isolated disease (yes vs no). After primary surgery, all patients receive 6 months of chemotherapy consisting of leucovorin calcium IV followed by fluorouracil IV over 10 minutes on days 1-5 every 4 weeks. Patients then undergo second look surgery or laparoscopy at 8-12 months. Second look surgery or laparoscopy may be performed earlier if markers increase progressively for unknown reasons or symptoms of peritoneal cancer occur. Patients with recurrent disease that can be resected are randomized to one of two treatment arms. Patients with no residual disease or with unresectable disease are followed for survival. Arm I: Patients undergo complete resection of all detectable lesions followed immediately by intraperitoneal (IP) mitomycin on day 0 and fluorouracil IP on days 1-4. Patients also receive systemic chemotherapy consisting of leucovorin calcium IV over 2 hours and fluorouracil IV bolus, followed by fluorouracil IV over 22 hours on days 1 and 2. Systemic chemotherapy repeats every 2 weeks for 6 months. Arm II: Patients undergo complete or partial resection and then receive systemic chemotherapy as in arm I. Quality of life is assessed at baseline and then every 4 months for 3 years. All patients (including nonrandomized patients) are followed every 4 months for 3 years.