In this study a direct comparison was made between power colour flow and frequency based colour flow Doppler in the visualization of the ventricular septum and the pulmonary veins of the fetal heart at 18 to 20 weeks. A total of 16 cases were scanned using both power colour flow and frequency based colour flow Doppler. The entire ventricular septum was visualized in all cases using power colour, but in only two cases using frequency based colour Doppler. However, frequency based colour Doppler was capable of identifying part of the ventricular septum in 14 cases. In the assessment of the pulmonary veins, power colour demonstrated both right and left pulmonary veins clearly in 12 cases. There were no cases in which both the right and left pulmonary veins were demonstrated using frequency based colour Doppler.