MRI has proven highly sensitive in detecting subtle abnormalities in cortical and subcortical brain parenchyma. While some of these abnormalities are associated with known neurologic disorders, many are unexpected or incidental. White matter lesions (WMLs), ventricular enlargement (VE), and sulcal widening (SW) are common findings in persons over age 50. Although these structural abnormalities have been associated with a number of cardiovascular and cerebrovascular risk factors, and in some studies with the presence of dementia, relatively few studies have examined the effects of these changes on cognitive performance in nondemented subjects. The present study examined the relationship between WMLs, VE, and SW and three measures of cognitive functioning (verbal memory, VM; verbal fluency, VF; and psychomotor speed; PS). Subjects were 1,571 individuals (age 55-72) participating in the cerebral MRI study conducted at two sites of the Atherosclerosis Risk in Communities (ARIC) study. ARIC is a longitudinal, epidemiological examination (sponsored by NHLBI) of the major factors contributing to the occurrence and trend of atherosclerotic disease in middle-aged adults in the US. The ARIC cohort is composed of a population-based, bi-racial sample of 15,800 men and women aged 45-64 (at inception) in four US communities (Forsyth County, NC; Jackson, MS; selected suburbs of Minneapolis, MN; and Washington County, MD). All participants over age 55 at two of the ARIC community Field Centers (Forsyth County, NC and Jackson, MS) were invited to receive a cerebral MRI examination. MRI data was read at the Johns Hopkins MRI Reading Center and graded for severity on a 0-9 scale. After controlling for age, education, gender, and ethnicity, SW was significantly associated with PS (p < .01), and VE was associated with PS (p < .001) and VF (p < .04). No effects were found for WMLs. Participant age was found to influence the magnitude of the associations observed between VE and the cognitive variables.