OBJECTIVE: The study examined the influence of losses in dopaminergic function on age-related cognitive deficits. METHOD: Eleven healthy subjects (21–68 years of age) completed a set of cognitive tasks used to assess perceptual speed and episodic memory. D2 receptor binding was measured in the caudate and the putamen by using positron emission tomography. RESULTS: A gradual age-related deterioration was found for all cognitive tasks and for D2 binding in both striatal structures. Statistical control of D2 binding eliminated the age-related cognitive variation, whereas residual effects of D2 binding were seen after the analysis controlled for age. CONCLUSIONS: D2 receptor binding is a more important factor than chronological age in accounting for variation in cognitive performance across the adult lifespan. Changes in dopaminergic neurotransmission play an important role in aging-related cognitive decline.