This paper outlines the basic principles of Doppler ultrasound as used in neonatal medicine. It explains the method's limitations and the extraneous variables which must be taken into account when interpreting Doppler velocity data. Not with standing the methods limitations the use of Doppler ultrasound in various neonatal conditions will be reviewed, in particular its use in asphyxia, hydrocephalus and research of neonatal cerebral haemodynamics.