Dipyridamole stress testing may be used in the diagnosis of coronary artery disease and risk assessment of patients who are unable to exercise. Although dipyridamole perfusion imaging has a good safety record, serious side-effects may rarely occur. We present a case in which dipyridamole induced high-grade atrioventricular (AV) block that responded promptly to intravenous aminophylline but not to atropine.