The size, shape, margins, and structure of the ovaries, as observed in 26 patients with polycystic ovarian disease were analyzed, and uterine/ovarian ratio (maximum antero-posterior diameter of uterine fundus divided for longitudinal diameter of ovary) was calculated. The maximum surface area of the organs ranged from 9.5 cm2 to 17.3 cm2 (average value 12.9 cm2). A "roundness index" (minimum diameter X 100/maximum diameter) was calculated in order to evaluate the shape: it ranged from a value of 100 in perfectly rounded ovaries to a value of 54 in ovaries of oval shape. The ovarian structure was characterized by many small cysts of the same dimensions in 19 cases; in two patients there was a predominant cyst; in five cases it appeared as many thick echoes arranged along parallel lines. The uterine/ovarian ratio was always equal to or less than 1. Correlation tests for size, shape of the ovaries, patient's age, and duration of symptoms were highly significant. This leads one to suppose that both of these ultrasonic findings are a function of the duration of the disease and that polycystic ovarian disease, once established, is the cause of progressive enlargement of these organs.