A cross-sectional study was conducted to determine whether normal, age-related declines in cognitive function are accelerated in non-insulin-dependent (type II) diabetes mellitus. Study participants ranged in age from 55 to 74 years. Results indicate that cognitive function is inferior in the patients with type II diabetes compared with a comparably aged, nondiabetic control group. On the basis of a series of cognitive tests, it appears that the cognitive impairment is due to a deficiency in memory retrieval rather than to an attentional or encoding deficit. Cognitive performance is poorer in diabetic patients with peripheral neuropathy or elevated hemoglobin A1c levels. The apparent cognitive impairment in aging patients with type II diabetes may complicate adherence to medical regimens.