Coronary atherosclerosis begins in childhood and is expressed in adulthood as angina pectoris, myocardial infarction, or sudden death. The earliest lesion in the vascular system is the fatty streak, characterized by an accumulation of lipids in the intima. These lesions are present in the vessels of infants and young children. Whether these fatty streaks are precursors of more complex lesions is controversial. However, fibrous plaques, intimal lesions consisting of a central core of extracellular lipids covered with a cap of fibromuscular tissue, are frequently seen in children by 15 years of age. In addition, necropsy studies of United States battle casualties confirm the presence of advanced coronary lesions in young adults. Thus, it appears that the atherosclerotic process is well established in the American population by young adulthood.