Reaction times (RT) typically are slower in demented individuals than in healthy older people, but it is unclear if this deficit is useful in diagnosing Alzheimer's disease, particularly in its early stages. In this study we compared 131 nondemented, 73 very mildly demented, and 45 mildly demented individuals on simple, choice, and choice with distraction RT tasks. Less than half of the demented individuals could be classified correctly using the RT measures in a discriminant function analysis. In addition, the RT measures did not add significantly to correct classification achieved by a previously identified brief battery of standard neuropsychological tests including immediate prose recall, confrontation naming, and digit symbol substitution (Storandt & Hill, 1989); that battery identified 81% of the very mild group and 96% of the mild group as demented. Although substantial slowing of RT may occur in some people in the early stages of dementia, it is far from universal, whereas deficits in other cognitive functions are.