Long-acting octapeptide somatostatin analogs can effectively control symptoms resulting from excessive hormone release in patients with endocrine tumors of the gastrointestinal tract, provided that these tumors and metastases show a high expression of the somatostatin receptor subtype 2. The presence of this receptor subtype on these tumors can be demonstrated by in vitro studies, but also in vivo using 111In-pentetreotide scintigraphy. In a few studies, significant antiproliferative effects of these drugs on these tumors have also been demonstrated. The effectiveness of octapeptide somatostatin analogs in the management of chemotherapy- related and AIDS-related diarrhea and in reducing postoperative complications of pancreatic surgery have also been demonstrated. These drugs have been used to decrease the output of enterocutaneous pancreatic fistulas and are prophylactically used to prevent the development of these fistulas. Octapeptide somatostatin analog therapy is widely accepted for the initial management of acute variceal bleeding in cirrhotic patients. These drugs are currently also being evaluated for the treatment of advanced hepatocellular carcinoma and malignant intestinal obstruction. Radiotherapy with octapeptide somatostatin analogs coupled to radionuclides such as indium-111, yttrium-90, and lutetium- 177 is currently being studied in phase I-III trials.