Intramural course of coronary arteries is a well known phenomenon on autopsy. On angiography, however, it is usually seen in relation to the left anterior descending artery. Clinically, this entity may be associated with myocardial ischemia, infarction or sudden cardiac death. In this case, we report an unusual angiographic finding of first septal branch of left anterior descending artery. We present the case of a 43-year-old man with clinical and exercise ECG evidence of ischemia, whose primary abnormality is systolic compression of a long segment of anomalous large first septal branch.