The first part gives an overview of the practical application of colour-coded Doppler sonography in foetal cardiology. After a comparison between colour-coded and pulsed spectral Doppler in the assessment of foetal intracardiac haemodynamics, the basic principles of colour Doppler are presented. Some practicl aspects important in the optimal analysis of the foetal heart are emphasised considering the possibilities and limits of the method. The typical patterns of colour Doppler flow in normal foetal hearts and possible pitfalls are explained viewing different cross-section planes. After the analysis of the cardiac structures in Real-Time, the colour Doppler sonography enables the examiner to assess rapidly and reliably the intracardiac haemodynamics in the foetus. This diagnostical mean improves the accuracy of foetal echocardiography in the diagnosis of congenital cardiac diseases.