Objective: The international, first-line diagnostic test for adult GH deficiency is the insulin tolerance test (ITT), which is contraindicated in some patients due to severe adverse events. Alternatives such as GH-releasing hormone combined with arginine or GH-releasing peptides (GHRP) have been proposed. We validated the use of GHRP-2 for diagnosing adult GH deficiency (GHD). Methods: Seventy-seven healthy subjects and 58 patients with peak GHResults: Serum GH peak occurred within 60 min after GHRP-2 administration in all subjects. GH responses to GHRP-2 were not affected by gender, but were slightly lower in elderly subjects and those with adiposity, although these did not influence diagnosis of GHD. Repeated tests showed favourable reproducibility. Peak GH concentrations after GHRP-2 were significantly (PConclusions: The GHRP-2 provocative test showed favourable reproducibility and was mildly influenced by age and adiposity. Severe GH deficiency could be diagnosed with high reliability using a 15 μg/l (9 μg/l when GH calibrated with recombinant World Health Organization 98/574 standard) cut-off for peak GH concentration.