Growth hormone (GH) has been in clinical use for almost 40 years to promote linear growth in growth hormone deficient children. Treatment has usually been stopped after the epiphyseal plates have fused or when the person reaches a proper height. Previously, GH replacement therapy in adults was not deemed clinically indicated. GH-deficiency in adults is now accepted as a clinical entity, manifested by cardiovascular dysfunction, dyslipidemia, reduced capacity for exercise and muscular weakness, altered body composition, increased prevalence of osteoporosis, and impaired psychological well-being. The treatment of adults used to be unrealistic, because of the limited supply of human pituitary-derived GH. Moreover, the risk of transferring Creutzfeldt-Jakobs disease led to a stop in the therapeutic use of pituitary GH preparations. The availability of recombinant human prion-free GH has made replacement therapy possible in GH-deficient adults. In this review, the GH deficiency syndrome in adults is described, together with the results of recent clinical studies of GH replacement treatment in adults.