Apolipoprotein (apo) A-I and apo B-100 were examined in 378 aging males for studying the relationship of apolipoprotein to cardiovascular diseases. The results showed that apo A-I and apo B-100 were 148 +/- 30 mg/dl, 97.3 +/- 28 mg/dl in the healthy aged subjects. Patients with CHD had the higher level of apo B-100 (P < 0.01) than the controls. Apolipoprotein A-I was decreased (P < 0.05), but apo B-100 was increased (P < 0.01) in the patients with hypertension which indicated that the change of apolipoprotein could be a factor for patients with hypertension and sensitive to CHD. There were a positive correlation between apo B-100 and apo A-I cholesterol contents (r = 0.22, P < 0.05) as well as a negative correlation between apo A-I and fibrinogen (r = -0.2, P < 0.05) contents. Our data suggested that a higher content of apo A-I and lower content of apo B-100 might serve as the protective factors for CHD.