The introduction and the continuing advances in fetal Doppler echocardiography have enhanced our understanding of the hemodynamic function of the fetal heart and extended our knowledge of the aberrations of this function in various cardiac disorders. The latter include congenital cardiac malformations, cardiac rhythm disturbances, and fetal heart failure. Many of these conditions in the context of Doppler sonography are discussed elsewhere in this text. It is apparent that the addition of the Doppler modality significantly enhances the diagnostic information that can be obtained from sonographic imaging of the fetal heart, and color and spectral Doppler echocardiography has now become an essential component of the fetal cardiac examination. In order to ensure the reliability of the technique it is imperative, however, that one should be thoroughly familiar with the instrumentation and rigorously trained in its application. When used appropriately, Doppler echocardiography remains a unique and powerful tool for fetal assessment in health and disease.