Growth hormone (GH). while primarily noted for its anabolic effects, has also been demonstrated to have effects on immune cell development and function. Receptors for GH have been found to be present on a variety of immune cell types and numerous effects on immune cell functions have been reported. With the advent of recombinant material, it has become possible to delineate the effects of GH under more stringent conditions. However. GH may exert many of its effects indirectly through the induction and release of IGF-1. In addition, many of the immune effects ascribed to GH in immune system development and function have utilized neurendocrine hormone-deficient dwarf animals, which are deficient in hormones other than GH. making interpretation concerning the role of GH in immune development and function difficult. In addition, human GH can bind the prolactin receptor. Recent data suggest that GH may have effects on immune cell function under periods of stress, either directly or through IGF-1, and may work in concert with other cytokines.