Thus far, somatostatin has been used primarily as a research tool to investigate pancreatic alpha- and beta- cell function. On the basis of its ability to inhibit insulin and glucagon secretion, several therapeutic applications have been suggested: e.g., as an adjunct in the treatment of diabetes mellitus, or as a palliative agent in inoperable islet tumors. Current experiments are underway to develop more specific analogs with longer durations of action to permit clinical evaluation of these potential applications. The presence of somatostatin within the pancreatic D cells raises the possibility that it may function as a local regulator of insulin and glucagon release. Clearly, further work is needed to delineate the factors governing the secretion of somatostatin and its mode of action. Such studies may uncover a new class of syndromes resulting from D-cell dysfunction.