The uteroplacental circulation of the cynomolgus monkey was examined in early pregnancy using a high-resolution ultrasound scanner. Intravenous injection of an echo-contrast agent, Albunex (sonicated albumin), was used to enhance the color Doppler images obtained. The flow of blood into and out of the intervillous compartment was readily assessed and quantified using pulsed and color Doppler. Flow within the intracotyledonary space was pulsatile and indicative of a low-resistance system. Flow within the decidual veins was non-pulsatile. The use of echo-contrast agents may assist in the determination of intervillous flow in human pregnancy at a correspondingly early stage.