Diabetic men (noninsulin dependent, Type II) in the Baltimore Longitudinal Study of Aging were compared with nondiabetics on two cognitive performance tests--the Benton Visual Retention Test, a measure of nonverbal memory, and the Vocabulary subtest of the Wechsler Adult Intelligence Scale. Cross-sectional comparisons of 52 diabetics with matched controls and with 610 controls (covaried for age and education) found no group differences and no support for an accelerated cognitive aging effect of diabetes. In addition, longitudinal comparisons over six years and over twelve years found no effect of diabetes on change in cognitive performance. Possible reasons for disagreements of cross-sectional findings in the literature are discussed. One possibility is that only specific aspects of cognitive performance are adversely affected by diabetes. It is also possible that lower socio-economic status (as indexed by education) may be a risk factor in the effect of diabetes on cognitive performance, perhaps by delaying diagnosis and treatment.