Background: The clinical significance of anomalously originating coronary arteries depends on their proximal course. Diagnosis of this course by conventional x-ray coronary angiography alone may be equivocal. We postulated that with fast magnetic resonance (MR) angiography, accurate detection of anomalous coronary arteries and unambiguous delineation of their proximal course is feasible. Methods and Results: In a selected group of 38 patients, 19 of them having an anomalously originating coronary artery, a fast MR angiographic technique was used to study the proximal coronary anatomy. Blinded analysis of randomly ordered MR studies was performed independently by two observers. Both origin and proximal course of the coronary arteries were defined. Two cardiologists reviewed all x-ray coronary angiograms. After the separate analyses, a final consensus result was defined for each patient. In 37 patients, successful MR coronary angiography could be performed. Interobserver agreement for determining both origin and proximal course was 100%. An x-ray coronary angiogram was available in 36 patients. In 3 patients (all with an anomalous left main coronary artery originating from the right aortic sinus), there was disagreement about the proximal course between the results of MR and x-ray coronary angiography had unambiguously visualized the proximal coronary artery course, whereas the results of x-ray angiography had been equivocal. Thus, sensitivity and specificity for detecting anomalous coronary arteries and delineating their proximal course were 100%. Conclusions: These data suggest that fast MR angiography is highly accurate in determining the origin and delineating the proximal course of anomalous coronary arteries, even in those cases in which x-ray coronary angiographic diagnosis is difficult or even erroneous.