Local myometrial and cervical uterine blood flow were measured repeatedly in 45 women by the hydrogen gas clearance method. Mean myometrial blood flow in the postmenopausal women was 57.5 * 6.67 ml/min. 100 g and in the women of fertile age 105.5 8.36 ml/ min.lOO g. When oxytocin was given intravenously between measurements, no effect on myometrial blood flow was obtained in the postmenopausal women. In women of fertile age, myometrial blood flow was reduced to 18.9+ 5.08% of controls in the proliferative phase and to 33.1 *7.62% in the secretory phase 2 minutes after injection of oxytocin, whereas cervical blood flow in both phases showed no or only a slight reduction.