The discovery and subsequent synthesis of growth hormone-releasing hormone (GHRH) has greatly advanced our understanding of the factors regulating growth. In this review we have given a brief historical account of the important events leading to the discovery of GHRH, and then discussed the physiology of growth hormone regulation. GHRH, given intravenously, provides a test of the “readily releasable” pool of pituitary GH, but although it can in some cases differentiate hypothalamic from pituitary causes of GH-deficiency, its role as a diagnostic test has not been fully defined. Preliminary studies suggest GHRH may provide an alternative treatment for short stature to GH, and the future development of a long-acting preparation of GHRH may provide an important advance in therapy.