The hormonal responses to surgical stress were examined in 10 patients scheduled for elective gynecologic laparotomy. Anesthesia was induced with either thiopental, 4 mg/kg, or etomidate, 0.35 mg/kg, and maintained with nitrous oxide and enflurane. Plasma cortisol, aldosterone, ACTH, and catecholamines were measured during the 24 h after the induction of anesthesia. The catecholamine responses of the patients whose anesthesia was induced with either drug were similar. The plasma ACTH concentrations for the etomidate group were greater than baseline values and the concentrations in the thiopental group (P< 0.05) in the fourth and fifth hours. In the patients receiving thiopental, both cortisol and aldosterone concentrations were greater than the baseline value (P< 0.05) in the second to fourth hours after induction. In the etomidate group, the plasma concentrations of cortisol were less than baseline values (P< 0.05) in the first and second hours after induction of anesthesia and both cortisol and aldosterone were lower than those in the thiopental group (P< 0.05) in the half to fourth hours after induction. These results confirm an earlier report of the suppression of cortisol after etomidate administration and, because aldosterone also was suppressed, suggests that etomidate exerts its effect by inhibiting early stages of steroidogenesis in the adrenal cortex.