THE INCREASING availability of human growth hormone (hGH) extracted from pituitary glands by both the National Hormone and Pituitary Program (formerly National Pituitary Agency) and commercial sources and the pending explosion of the supply of hGH manufactured by recombinant DNA technology provides a backdrop for this review of hGH therapy in growth hormone deficiency. As the supply of hGH grows and the number of patients receiving this material expands, it should be helpful to look at the information which has been accumulated in this area over more than 20 years. I will attempt to present a comprehensive review of growth hormone therapy which will develop at least some answers to the large number of questions which remain despite a very extensive collective experience. Successful treatment of growth hormone deficiency with hGH was initially reported by Raben in 1958 (1). Scattered additional reports of hGH therapy subsequently appeared (2–8), and by 1964 it was clear that hGH stimulated linear growth in patients with growth hormone deficiency.