A study carried out on the coronary arteries of 536 subjects ranging in age from 0 to 40 years demonostrated that males exhibited, as compared to females of similar age: more numerous and extensive severe changes of the internal elastic membrane, particularly in neonates and children; a thicker intimal layer in all age-groups investigated; an earlier development of atherosclerotic plaques and of atheroma-like lesions; a higher number of cases with coronary atherosclerotic plaques; a more precocious and diffuse extension of atherosclerotic plaques in the whole coronary tree.