We present a review of data from epidemiological and morphological studies carried out in Kaunas of atherosclerosis in youths. Since 1985, Kaunas has been a Collaborating Center involved with the World Health Organization and International Society and Federation of Cardiology studying the pathobiological determinants of atherosclerosis in youth. During the pilot study (1985-1987), we estimated the prevalence and extent of atherosclerotic lesions in the aorta and coronary arteries correlated to various risk factors in Kaunas residents aged 5 to 44 years. Within the framework of this international study, we compared histomorphometric characteristics of arteries collected from trauma victims aged 5 to 34 years in Budapest (Hungary), Heidelberg (Germany), Kaunas (Lithuania), Yaounde (Cameroon), and Mexico City (Mexico). These data revealed that males from countries with a high mortality from ischemic heart disease (Hungary, Lithuania, Germany) tended to have thicker intima in the thoracic and abdominal aorta and left anterior descending coronary artery than did males from countries with low mortality from ischemic heart disease (Mexico, Cameroon). We detected an increased mean intimal thickness of the abdominal aorta in male smokers aged 25-34 years. Males with hypertension aged 15-24 and 25-34 years had a thicker intima in the aorta and left anterior descending coronary artery than normotensive males. The morphological and epidemiological studies of atherosclerosis in youths carried out in Kaunas demonstrated that aortic and coronary atherosclerotic lesions appeared as early as childhood and advanced until the lesions become clinically apparent in adulthood. Histomorphometric findings support the postulate that increased intimal thickness can be considered a structural determinant of atherogenesis. These data draw attention to the means for the primary prevention of atherosclerosis in youth.