Age-cohort differences for seven tests from the Halstead-Reitan Neuropsychological Battery, for overall performance on the Impairment Index, and for a multivariate composite of the seven scores, were examined for 427 subjects falling into six age groups (15-24, 25-34, 35-44, 45-54, 55-64, and 65 years and over). Univariate and multivariate-discriminant analyses were performed. Poorer performance was observed across age-cohorts (linear trend) for all tests and the Impairment Index. A very modest Age-Cohort (linear trend) x Gender interaction was observed only for the Category Test. Decline in Category Test performance across age-cohorts was more pronounced for women than for men. For women, the best discrimination among age groups was observed for the Category Test. For men, Tactile Performance Localization Test discriminated best. The poorest discrimination among age groups was seen for Finger-Tapping for men and Tactile Performance Test--Total (time score) for women. Results were consistent with a model of specific nested within general decline. Although linear-trend across age groups was observed for all tests, the strongest discriminations were associated with neuropsychological tests of abstraction and complex problem-solving performance.