Ninety-five adolescents with menstrual irregularities persisting since menarche were studied and the data analyzed in relation to gynecologic age. In each year, in the premenstrual phase, luteinizing hormone (LH), testosterone (T), and androstenedione (delta 4A) values were higher than those of adults. Estrone (E1), estradiol (E2), 17-hydroxyprogesterone (17-OHP), progesterone (P), and dehydroepiandrosterone (DHEA) and its sulfate (DHEAS) gradually increased up to adult values correlating with gynecologic age. By ultrasound, nearly half the ovaries were multicystic and ovarian volume was greater than that of adults in each gynecologic year. When the data were classified as ovulatory or anovulatory, ovulation appeared to be a dynamic process characterized by ovaries similar to those of adults and by increasing hormonal levels correlated to gynecologic age. By contrast, in anovulatory cycles, mean T, delta 4A, and LH values were stable in each year and constantly higher than in ovulatory cycles and adult controls. These findings suggest that, despite persistent irregular cycles, some adolescents normalize all endocrine and ovarian parameters toward maturity, while subjects with persistent irregular anovulatory cycles maintain marked hyperandrogenism, increasingly high LH values, and enlarged multicystic ovaries.