Summary: The transvaginal ultrasound appearances of the ovary were determined in women with clinical and endocrine features of polycystic ovarian disease (PCOD) and apparently normal women. At scan the number of small follicles were counted and ovarian volume was calculated. The maximum width of the ovarian cortex was also measured. Blood was sent for measurement of LH, FSH and testosterone. The women with oligomenorrhoea were scanned at random and the normal women were seen within the first 5 days of the start of menstruation. There were significant differences between median values for the 2 groups in terms of number of small follicles, ovarian volume and stromal width; the ovaries of the hirsute women had more follicles, were of larger volume, and had greater stromal width. The 2 ranges for number of follicles did overlap, however. Four hirsute oligomenorrhoeic women had a normal number of follicles; all 4 had the several clinical and endocrine features indicative of PCOD. These data suggest that the classical ultrasound features of PCOD are not consistently present and that the absence of increased follicularity at scan should not necessarily deter clinicians from making the functional diagnosis of PCOD.