A pulsed Doppler ultrasound velocity meter was used to measure blood velocities in the right uterine artery and a mammary branch of the right lateral thoracic artery in one subject throughout pregnancy and after parturition. The breast blood velocity was also followed throughout lactation. The velocities in the uterine artery increased 2.5-fold from the 15th to the 38th week, when delivery occurred. An estimate of the total blood flow in the uterine artery, based on the total intensities in the Doppler spectrum, increased 5-fold in the same period. This corresponds to the increase in volume flow obtained with invasive methods. Velocities in the breast artery increased 2.5-fold from the 12th to the 25th week of pregnancy and then stayed at the same level throughout lactation; after weaning, they rapidly declined.