We describe an unusual case of acute septal myocardial infarction in a heart transplant recipient. The clinical presentation was most suggestive of acute rejection; the correct diagnosis was first made by endomyocardial biopsy and was then verified by coronary angiography. Acute myocardial infarction should be included in the differential diagnosis of acute rejection after heart transplantation and included among the possible diagnoses made by endomyocardial biopsy in these patients.