Pelvic ultrasonography was performed on 25 adolescent patients with menstrual disorders and/or hirsutism. Clinical and endocrinologic state was evaluated by history, physical examination and assays of serum LH, FSH, prolactin, testosterone and androstenedione levels in order to determine a possible association between hormonal levels and ovarian volume in the etiologic investigation of these adolescent girls. Patients aged 12 to 19 years, mean 14.92 years (menarche at 12 to 16 years; mean, 12.32 years) were divided into three groups according to ovarian size at ultrasonography: group I, N = 13, both ovaries 2-10 cm3; group II, N = 5, one of the ovaries > 10 cm3; group III, N = 7, both ovaries > 10 cm3. A strong correlation between serum LH levels and ovarian volume (r = 0.647, P < 0.0001) was observed. Moreover, when comparing the hormonal levels of all three groups, serum LH levels were significantly higher in group III (group I, 3.92 +/- 3.49; group II, 5.25 +/- 2.71; group III, 9.77 +/- 3.11 mIU/ml; mean +/- SD, P < 0.003) while testosterone and androstenedione levels showed a tendency to also be higher, but this difference was not significant. This hormonal pattern is suggestive of polycystic ovary syndrome (PCOS). The present results suggest that ovarian size of more than 10 cm3 at pelvic ultrasound in adolescent girls with menstrual disorders and/or hirsutism might be predictive of PCOS and emphasize the importance of careful assessment of ovarian volume by ultrasound.