Serum apolipoprotein (apo) E levels and their relationship with age were examined in different age groups of healthy individuals of both sexes in a Lithuanian population. The serum concentrations of apo E in patients after coronary bypass were measured and patients suffered from diabetes mellitus were also examined. The mean levels of apo E were found to be higher in healthy males than those in healthy females only in young age. Serum apo E levels were inversely associated with age (P < 0.05). Apo E levels were significantly higher in males over 45 years of age who suffered from coronary atherosclerosis and in males under 45 who had diabetes mellitus (types I and II) than those in healthy individuals (P < 0.05). There was an insignificant difference in apo E levels among healthy and diabetic females (P < 0.05). The findings demonstrated the association of increased apo E levels with atherogenesis.