Although coronary artery disease (CAD) is not common among individuals younger than 40-45 years of age, a small percentage of this age group needs to undergo surgical revascularization because of CAD. Why some people are at higher risk of developing premature CAD is not clearly known. Increased number of traditional risk factors or genetic predisposition may play significant roles in this regard. A 22-year-old man with a negative history for all traditional risk factors except for a family history of premature CAD referred to our center due to an episode of myocardial infarction of one month's duration. He had no congenital heart disease and no hypercoagulable state, and there was a negative history of drug abuse. His coronary angiography showed extensive CAD. He underwent coronary artery bypass grafting and he left the hospital in good healthy condition. One year after surgery, his follow-up showed that he was symptom free and he still had no new traditional risk factor. It seems that a positive family history of premature CAD is an important and independent risk factor for developing premature CAD and individuals with this type of history should be treated more cautiously.