Somatostatin is a small cyclic peptide with antiinflammatory and immunoregulatory properties. It is made by nerve, endocrine, and inflammatory cells. Somatostatin and somatostatin agonists inhibit inflammation in several animal model systems and in human diseases. Somatostatin acts on T cells to inhibit antigen-stimulated IFN-gamma release. It is made by activated macrophages within inflammatory lesions. Cytokines such as IFN-gamma or IL-10 and inflammatory mediators such as LPS or prostaglandin E2 induce normal splenic macrophages to make somatostatin. Somatostatin is a highly conserved peptide that functions as a neurotransmitter, a hormone, and an inducible immunoregulatory cytokine.