Aerobic activity performed on a regular basis is 1 of several lifestyle recommendations endorsed to reduce risk of coronary disease. However, 1 potential concern of arduous aerobic activity is exercise-induced hypertension. This is the first case to our knowledge, of accelerated coronary calcification in an otherwise asymptomatic middle-aged male marathon runner devoid of traditional cardiovascular risk factors. As a consequence of exercise-induced hypertension and associated oxidative stress, improvement of endothelial dysfunction occurred after antioxidant supplementation. In conclusion, vigorous aerobic activity in susceptible individuals may promote oxidative stress and coronary atherosclerosis.