Clinical symptoms and age at manifestation of a congenital coronary artery fistula may vary considerably. They depend on the underlying anatomy and also on the size of the fistulous connection to the left or right side of the heart. Using colour Doppler echocardiography for direct visualization of the entire course of the fistulous vessel, including the site of termination, succeeds only in a small number of cases. Furthermore, regular coronary vessels branching off proximally and distally of the coronary artery fistula usually are not recognizable by this method. Only selective angiography provides this information and is unchallenged the most important and indispensable diagnostic technique, especially with regard to surgical treatment. This publication presents physical, echocardiographic, and angiographic data of 15 patients, who were admitted to the German Heart Center Munich between 1970 and 1993. By an invasive diagnostic approach the following arteriovenous fistulous connections were found: from right coronary artery to right atrium (3 patients) or to right ventricle (3 patients), from left coronary artery to right atrium or coronary sinus (3 patients), from left coronary artery to right ventricle (4 patients) and from right and left coronary artery to right ventricle (2 patients). In 5 patients a "proximal" form of coronary artery fistula ("side-to-side pattern") was found, in 8 patients a "distal" form ("end-artery type"), and in 2 patients a combination of both forms. In 14 patients surgical closure was performed (6 symptomatic infants, mean age at surgery = 95 days, and 8 asymptomatic children, mean age at surgery = 7.1 years): 13 patients survived surgery. On an average of 5 years after surgery all of these 13 patients are in excellent condition (NYHA functional class I). The experiences in surgical treatment verify the importance of an exact angiographic visualization of the anatomy of a coronary artery fistula and the regular coronary vessels branching off proximally and distally of the fistula. Closure of coronary artery fistulas at the time of diagnosis is recommended also in asymptomatic patients, since perioperative morbidity and mortality increases in older patients.