Transvaginal ultrasound examinations were performed in 37 oligo- or a-menorrheic women to describe ovarian changes and potential correlations with clinical and some biochemical features of polycystic ovarian syndrome (PCOS). Findings were compared between the right and left ovary and between each of three subsequent examinations of the same ovary. In any one ovary, no significant difference was found between mean ovarian volume, stroma echogenicity, mean follicle number and size. Correlation between ovarian volume and follicle number was strong in all examinations. Follicle number in both ovaries correlated significantly with ovarian stroma echogenicity and some biochemical markers of PCOS. These observations validate the usefulness of transvaginal sonography in demonstrating numerous correlations in menstrual cycle disturbances. The strong necessity to reevaluate sonographic criteria of PCOS is highlighted.