In order to assess the role of growth hormone in the modulation of alpha cell function, the plasma pancreatic glucagon response to intravenous arginine (0.5 g/kg) was determined in thirty-two children with non-endocrine short stature and in eighteen growth hormone deficient children. 60 min after arginine infusion, the growth hormone deficient children had significantly higher (P less than 0.05) plasma glucagon values than the children with non-endocrine short stature. Following short-term growth hormone therapy (2 iu qd or bid for 5 days) in eleven of these growth hormone deficient children, plasma pancreatic glucagon response to arginine was diminished, and there was a significantly (P less than 0.02) more rapid return to basal values than in the untreated group. The same trends persisted after long-term growth hormone therapy (2 iu three times per week for 12-30 months) in ten children but were not statistically significant. We conclude that growth hormone may play a role in modulating plasma pancreatic glucagon response. The persistent glucagon response to arginine noted in growth hormone deficient children might reflect a greater gluconeogenic stress imposed upon these children during fasting or decreased catabolism of glucagon in the growth hormone deficient state.