We combined two ultrasound techniques to develop a safe, non-invasive, transcutaneous method of observing the circulation in the umbilical arteries and vein in the fetus. The umbilical cord can be located by standard echo ultrasound procedures, and this information can be used to direct a Doppler ultrasound beam on to the vessels in the cord. The signals can be heard through audio headphones or recorded on a tape recorded and spectrum-analysed. The method was successful in each of 20 patients examined, whose pregnancies ranged from 12 to 40 weeks' gestational age, and was suitable for outpatient use. It should be useful in assessing such conditions as pre-eclampsia and intrauterine growth retardation.