In brief: Sudden death during or following exercise is a dramatic event. In people over 40 years of age, coronary artery disease Is implicated in nearly 90% of exercise-related deaths. For those under 30 years of age, hypertrophic cardiomyopathy, abnormal coronary arteries, and coronary artery disease are the largest contributors. The authors report a case of myocardial infarction during exercise in which no clear cause could be determined. Only three similar cases have been previously reported. The authors speculate that coronary artery spasm was the cause, and they provide a literature review on sudden death and exercise.