With the in vivo demonstration of somatostatin-receptor- positive tumors in patients using a radiolabeled somatostatin analog, peptide receptor scintigraphy became available some 15 yr ago. Octreoscan is a radiopharmaceutical with proven clinical importance in the visualization of somatostatin-receptor-positive tumors, and the overall sensitivity of somatostatin receptor imaging is high. In a number of neuroendocrine tumor types, as well as in Hodgkin's disease, inclusion of somatostatin receptor imaging in the localization or staging procedure may be very rewarding. The value of somatostatin receptor imaging in patients with other tumors, like breast cancer, or in patients with granulomatous diseases, has to be established.