Short-term, high-dose oral glucocorticoid therapy is often required for control of acute asthma episodes in children. To evaluate possible hypothalamic-pituitary-adrenal (HPA) axis suppression after such therapy, we studied 11 children with just asymptomatic asthma before and at 3 and 10 days after completion of a five-day course of prednisone (up to 2 mg/kg/day in divided doses, maximum dose = 60 mg/day). HPA axis responsiveness was tested by measuring plasma corticosteroid levels before and after insulin-induced hypoglycemia. When these levels were compared to pretreatment levels, there was a statistically significant blunting of the peak corticosteroid responses to hypoglycemia 3 days after completion of the course of prednisone (p less than 0.001). However, corticosteroid responses were normal in all children 10 days after completion of the course of prednisone. We concluded that a single course of short-term, high-dose glucocorticoid therapy in children with asymptomatic asthma produces only transient (less than 10 days) HPA axis suppression.