A screening neurologic examination capable of detecting distal symmetric (sensory) neuropathy in a large population-based study of non-insulin-dependent diabetes mellitus in San Luis Valley, Colorado, in 1984-1986 is described and validated. The examination, completed in 279 diabetics and 577 controls, had 90% agreement with a standard neurologic examination completed on a subsample of 38 patients. Independent validation of neuropathy status was obtained with the Optacon tactile (vibration) stimulator. Mean, age-adjusted vibration threshold was significantly greater in those with neuropathy than in those without. The subtests of the examination most sensitive in detecting neuropathy were a combination of a positive history of neuropathy symptoms and decreased or absent deep tendon reflexes in both ankles. Age-adjusted prevalence of neuropathy in controls, those with impaired glucose tolerance, and diabetics was 3.9%, 11.2%, and 25.8%, respectively. Prevalence odds ratios were 3.5 and 10.6 for the presence of neuropathy in persons with impaired glucose tolerance and diabetes, respectively, compared with persons with normal glucose tolerance. Neuropathy was significantly associated with age, duration of diabetes, male sex, and glycemic control, but not with Anglo/Hispanic status.