To examine the relationship between systemic immune status and carotid atherosclerosis in elderly men, differential leukocyte counts and lymphocyte subpopulations were measured in 557 apparently healthy Japanese men aged 60-75 years. Each individual also underwent high-resolution ultrasonography for measurement of intima-media thickness (IMT) of the common carotid arteries. The increased numbers of circulating lymphocyte subpopulations, including memory T cells (CD4+CD45RO+T cells) and late-phase activated B cells (CD19+CD80+B cells) correlated significantly and positively with the mean IMT of the common carotid artery after adjustment for age, smoking, and other cardiovascular risk factors. The positive associations of CD19+CD80+B and CD4+CD45RO+ T cell counts with mean IMT were more evident among nonsmokers, hypertensives, and men with lower HDL-cholesterol levels. The present epidemiological study provided the evidence that alterations in lymphocyte subpopulations, in particular memory T cells and late-phase activated B cells concur with carotid atherosclerosis among free-living elderly men.