It is now accepted that adults with severe GH deficiency (GHD) demonstrate impaired physical and psychological well-being and may benefit from replacement with recombinant human GH. Post-marketing surveillance surveys, such as the Pfizer International Metabolic Database (KIMS), were initially set-up to provide safety data on long-term treatment but have the added benefit of providing ongoing observational data on the effect of GH replacement on body composition, lipid and glucose status, hypertension, bone density and quality of life. These data demonstrate that although GHD has clinical impact at all ages, the individual consequences of this condition may take on greater significance at different stages in life. At all ages, accurate, safe diagnosis and appropriate GH dosing are necessary to provide the individual with the best possible outcome.