Synacthen test has been widely used as a screening test for evaluation of adrenal cortisol reserve. We investigated whether depot Synacthen test can be used in place of short Synacthen test in the evaluation of cortisol reserve of the adrenal gland. The study included 20 healthy volunteers of both sexes. We examined plasma cortisol response 30, 60, 90, and 120 min after administration of plain Synacthen, 250 micrograms, iv (Group 1), and depot Synacthen, 1000 micrograms, im (Group 2). Peak cortisol values were statistically similar between the groups. The increment in cortisol levels following Synacthen was also similar between the groups. A plasma cortisol value above 550 or 600 nmol/L was achieved in both groups during the test of 90 or 120 minutes duration, respectively. We think that depot Synacthen test, im 1000 micrograms, may be used in place of plain Synacthen, iv 250 micrograms, for evaluation of adrenal cortisol reserve.