Adrenal function was evaluated in fourteen cancer patients receiving chemotherapy which included short-term high-dose courses of prednisone. 90 min corticotropin stimulation tests were performed before therapy and 1, 2, 4, and 7 days after steroids were discontinued. Responses were evaluated by standard criteria of adrenal function and by measurement of the intergrated cortisol response to corticotropin over 90 min. Thirteen of fourteen patients had suppressed adrenal function for at least 24 h. Although in most patients adrenal function had returned to normal between day 2 and 4, in five patients it remained suppressed for 7 days or more. Suppression did not correlate with either steroid dose or duration of therapy. Four of five patients receiving only 5 days' therapy showed evidence of adrenal suppression. Although overt clinical adrenal insufficiency after steroid administration is rare, these results indicate that adrenal function is suppressed more regularly after short-term high-dose steroid therapy than has been appreciated.