Pellets of glass (control), progesterone (P), testosterone (T), and estradiol-17beta (E) were placed on the mesentery or subcutaneously in the flank in ovariectomized (O) and ovariectomized-hysterectomized (OH) mice, insuring that all or most of the hormone would pass through the superior mesinteric or circumflex iliac veins. After 21 days the diameters of these and of the ovarian, uterine, and femoral veins and inferior vena cava were measured at autopsy. T and E caused significant enlargement of the uteri; E was also responsible for bladder distention. The ovarian and uterine veins enlarged significantly in mice treated with T and E as compared to the controls. All other veins failed to respond to P, T, and E. The evidence demonstrates a specific response of ovarian and uterine veins in O and OH mice to T and E.