This study examined whether participation in leisure activities during early and middle adulthood was associated with reduced risk of Alzheimer's disease. The sample consisted of 107 same-sex twin pairs discordant for dementia and for whom information on leisure activities was self-reported more than 20 years prior to clinical evaluation. A factor analysis of these activities yielded three activity factors: intellectual-cultural, self-improvement, and domestic activity. Matched-pair analyses compared activities within the discordant twin pairs while controlling for level of education. For the total sample, participation in a greater overall number of leisure activities was associated with lower risk of both Alzheimer's disease and dementia in general. Greater participation in intellectual-cultural activities was associated with lower risk of Alzheimer's disease for women, although not for men.