The release of cortisol, 17 alpha-OH-progesterone, androstenedione and testosterone during a standardized ACTH-stimulation test was investigated in three different stage of the normal menstrual cycle, to conclude if there is any stage dependency on the release of these hormones. No statistically significant differences were observed between the three stages concerning cortisol and testosterone increase. The increase of androstenedione in the pre-ovulatory stage was significantly high than that seen during the early follicular phase of the cycle. The increase of 17 alpha-OH-progesterone in the luteal phase was significantly less than that of both the early and late follicular stages of the cycle. Progesterone levels showed a small, but significant increase after ACTH-stimulation, in both the early and late stage of the follicular phase. However, the levels remained within the normal range of the follicular phase. In the luteal phase no increase was seen after ACTH-stimulation. Oestradiol-17 beta levels did not change at all after ACTH stimulation. The stage dependency of androstenedione and 17 alpha-OH-progesterone is discussed. The described stage-dependency different increase of 17 alpha-OH-progesterone release can be of importance when the results of ACTH-tests are evaluated to detect carriers of congenital adrenal hyperplasia.