Coronary arteriovenous fistulas are rare anomalies resulting in abnormal communication between the coronary artery and any chamber of the heart. An asymptomatic patient was referred for evaluation of her murmur. Two-dimensional and color Doppler echocardiographic evaluation revealed an enlarged left main coronary artery. A retrograde, eccentric small jet was found within the right ventricular outflow tract at the pulmonary artery valvular level allowing us to detect the entrance site of the fistula. The diagnosis was confirmed by cardiac catheterization and angiocardiography. Although our case was asymptomatic, the decision to perform cardiac surgery was made because of the aneurysmatic appearance of the left coronary artery. In our opinion, visualization of coronary arteries by two-dimensional echocardiography, together with additional information obtained from the Doppler examination, provides an excellent technique for the noninvasive diagnosis of coronary artery fistula.