The tetradecapeptide, somatostatin, initially shown to inhibit the release of growth hormone, also suppresses the release of glucagon, a fact that has suggested the use of this peptide as a therapeutic agent in the treatment of diabetes mellitus. 1 However, the potential for somatostatin itself to be used successfully in the treatment of diseases is severely limited by a short biological half-life, and it has been given by infusion in most studies of pancreatic hormone suppression both in animals and humans. Recently, we have reported a somatostatin analog, Wy-40,770, which suppressed growth hormone release in rats for 4 hr following a single subcutaneous injection. 2 This peptide lowered plasma growth hormone levels at 15 min, but had little effect on glucagon and insulin levels. The present paper describes another somatostatin analog, Wy-40,793, with extended biological activities. This analog is a potent suppressor of rat growth hormone release for 5 hr, and lowers both plasma glucagon and glucose levels in streptozotocin diabetic dogs for 3 hr. ▪