Cognitively stimulating experience is thought to contribute to cognitive reserve. We constructed a questionnaire consisting of 25 items about frequency of participation in cognitive activities across the life span and administered it to two groups of older persons. The total score on the scale had high internal consistency (coefficient alpha = 0.88) and temporal stability over a 4-week re-test interval (r = 0.79), and it was positively correlated with education. In analyses controlling for age, sex, and education, more frequent cognitive activity was related to better perceptual speed, visuospatial ability, and semantic memory but not to episodic memory or working memory. The results suggest that the scale provides a psychometrically sound measure of frequency of cognitive activity across the life span.