From a series of 4,313 consecutive patients who underwent a diagnostic coronary angiogram, 16 (0.37%) presented a congenital anomalous origin of the coronary arteries. None of these patients had other congenital cardiac anomalies associated. Age was 57 +/- 9 years and 13 (81%) were male. The diagnostic catheterization was performed for unstable angina in 8 patients (50%), for stable angina in five (32%), for dyspnea in two and for atypical chest pain in the remaining patient. A previous myocardial infarction was present in 6 patients (37%) whereas one patient had apical hypertrophic cardiomyopathy. We observed absence of coronary lesions in 4 patients and severe coronary stenosis lesions in 12 patients (75%), five of those with lesions located in the anomalous vessel. The most frequent abnormality found was an anomalous origin of left circumflex coronary artery in 8 cases (50%), followed by an abnormal origin of the right coronary artery in 5 cases (31%), and an abnormal origin of the left coronary tree in 3 cases (19%) (left anterior descending coronary artery arising from the right coronary artery, a single coronary artery which originated in the left coronary sinus, and a left main coronary artery which originated in the noncoronary sinus). The relationship of the anomalous coronary artery to the great vessels was the following: A retro-aortic course in 11 patient (69%), by the anterior free wall in two (12.5%), interarterial in two (12.5%), and septal in one (6%). Finally, as an index of the difficulty to visualize the anomalous coronary artery, an unusual catheter was needed in six (37%) of the diagnostic procedures to reach the target vessel.(ABSTRACT TRUNCATED AT 250 WORDS)