OBJECTIVE By using vaginal endosonography, ovarian stromal hypertrophy has been shown to be a strong diagnostic feature of polycystic ovarian syndrome and related states. However, this sign is difficult to quantify and to correlate with other findings because of its subjectivity. We have evaluated the use of computer assisted analysis of ultrasound scans to provide more objective measurements of ovarian structure and size. METHODS We used a computer assisted method for the reading of ultrasound scans. It allowed selective calculation of the stromal area by subtraction of the cyst area from the total ovarian area on a longitudinal ovarian section. METHODS A consecutive series of 57 patients with hyperandrogenism (group 1), 17 patients with hypothalamic anovulation (group 2) and 20 normal women (group 3). RESULTS By computerized measure, 75% patients from group 1 had a bilateral stromal area above the mean +2 SD (700 mm2) of women from group 3. All patients from group 2 were below this threshold. Serum LH level was above the normal range in 45% patients from group 1. The stromal area correlated positively with the serum delta 4-androstenedione (r = 0.47, P < 0.005) and 17 alpha-hydroxyprogesterone (r = 0.39, P < 0.005) levels, exclusively in group 1. It did not correlate with the basal serum testosterone, LH or insulin levels. The cyst area did not correlate with any hormonal parameter. CONCLUSIONS Ovarian stromal hypertrophy is a frequent and specific feature of hyperandrogenism. It correlates with the ovarian androgenic dysfunction. Its presence is not always linked with elevated serum immunoreactive LH levels. Further data are needed to elucidate the role of insulin and ovarian growth factors.