We examined the prospective association between cognitive ability in early adulthood and erythrocyte sedimentation rate, a marker of inflammation, in middle age. Participants were 4256 male Vietnam era US veterans. Data on cognitive ability, assessed by the Army General Technical Test, ethnicity, and place of service were extracted from enlistment files. Smoking behaviour, alcohol consumption, basic socio-demographics, and whether participants suffered from a physician diagnosed chronic disease were determined by telephone interview in middle-age in 1985. Erythrocyte sedimentation rate, cholesterol, blood pressure, height, and weight were measured at a 3-day medical examination in 1986. In linear regression models that adjusted for age and then additionally for circumstantial, socio-demographic, lifestyle, and health factors, poor cognitive ability in early adulthood was associated with greater erythrocyte sedimentation rate in middle age, ß=-.09. Thus, it would appear that not only does systemic inflammation influence cognition, but also that poor cognitive ability earlier in life is associated with inflammation in middle-age.