OBJECTIVE: This study was aimed to obtain information on normal MIS serum levels according to menstrual cycles of adult normal cycling women . It was also designed to obtain information on the ontogeny of the production profile of MIS and the pattern of its localization in ovary from adult normal cycling women. METHODS: Between January 1998 and January 1999, normal MIS serum levels were measured according to menstrual cycles using 160 serum samples from adult normal cycling women by ELISA. The ontogeny of the production profile of MIS and the pattern of its localization were also studied by immunohistochemical staining using the rabbit polyclonal antibody against human recombinant MIS in 35 ovarian specimens from adult normal cycling women. RESULT: The MIS levels were gradually increased through the follicular phase, reaching at its maximum at the ovulatory phase(4.2+/-2.6 ng/ml), and sharply decreased at the beginning of the luteal phase being minimized at the premenstrual phase(0.5+/-0.2 ng/ml). In average, the MIS levels of the follicular phase(3.7+/-1.9 ng/ml) were significantly higher than those of the luteal phase(1.8+/-2.4 ng/ml)(P<0.05). The MIS levels of the preovulatory and ovulatory phase were significantly higher than those of the other cycle days(P<0.05). Even the early follicular phase(2.9+/-1.6 ng/ml) showed higher MIS levels than the advanced luteal phase(0.9+/-0.7 ng/ml) and the premenstrual phase(0.5+/-0.2 ng/ml)(P<0.05 and P<0.05, respectively). The first staining for MIS was detected in the cytoplasm of granulosa cells when the flattened granulosa cells changed to the cuboidal cells in primordial follicles. The granulosa cells of both single and multiple layered growing follicles showed strong specific staining for MIS. but the MIS staining was not found not in the mature follicle just before ovulation, atretic follicles, corpus luteum, and corpus albicans. MIS staining waned in the mature follicles just before ovulation. CONCLUSION: These experiments demonstrate that the MIS is produced by ovarian granulosa cells in normal reproductive females. The MIS may play an important role as a hormone of follicular development and oocyte maturation through interactions with female steroid hormones, gonadotropins, and growth factors during the adult reproductive cycle.