Patients with histologically proven gastrointestinal adenocarcinoma, mesothelioma, or sarcoma. By standard staging studies there must be evidence of advanced or metastatic intraabdominal disease. Patients with minimal extraabdominal metastatic disease and who have symptoms exclusively referable to advanced intraabdominal malignancy will be considered for the study. Specifically, patients with gastric cancer and bulky N-2 lymph node involvement or patients with other primaries and who have malignant ascites or peritoneal seeding would be considered optimal candidates. If all gross peritoneal disease is resected (i.e., gross omental implants removed by gastrectomy), patients are still eligible for treatment.