Two-dimensional echocardiography has developed to the routine examination to diagnose congenital heart disease. In this study, we studied the value of two-dimensional echocardiography for evaluating the development of the fetal heart and for prenatal diagnosis of congenital heart disease. We studied 100 fetuses whose gestational ages were 16-40 weeks of pregnancy. The examination was performed with Toshiba Sonolayer-V model SSL-53M. The scanners were the 2.25 MHz linear and sector transducers. The images were recorded on videotapes. Changing the scanner direction according to the fetal position, we recorded the left ventricular long-axis view, short-axis view of great arteries and four-chamber view. In the four-chamber view, diameters of the tricuspid and mitral valve rings were measured. In the short-axis view of great arteries, the diameters of the aorta and pulmonary artery were measured. We identified the right and left ventricles by detecting both the great arteries and attaching sites of the atrioventricular valves. The identification of the aorta was made by detecting the arch and the identification of the pulmonary artery was made by depicting its two branches. Cardiac structures were identified on the fetus over five months of pregnancy. In many instances recordings were obtained in 7 months fetuses. The success rate to get clear recordings was 88% of all cases in the four-chamber view, 75% in the short-axis view of great arteries and 71% in the left ventricular long-axis view, respectively. The average ratio of the mitral to tricuspid valvular diameter and that of the pulmonary arterial to aortic diameter were both less than 1, suggesting the right ventricular dominance in fetal hearts. From these findings, it might be possible to diagnose prenatally certain congenital heart diseases such as atrioventricular valve atresia and semilunar valve atresia which require the critical evaluation and management in the neonatal periods.