OBJECTIVES: To assess whether cataract surgery has an effect on cognitive function in older adults. DESIGN: Longitudinal. SETTING: Assessment of patients seen in eye clinics. PARTICIPANTS: Patients with no cataract (n = 92), patients with cataract who elected surgery (n = 122), and patients with cataract who declined surgery (n = 87). MEASUREMENTS: At baseline and 1-year follow-up visits, the following information was obtained: demographic, health behavior, general health status, medication use, depressive symptoms, cognitive function, and visual function information. This information was compared within and between groups at baseline and follow-up visits. RESULTS: Mattis Organic Mental Syndrome Screening Examination scores at baseline and follow-up varied across the three groups, with the cataract/no surgery group having the highest scores (more cognitive impairment) and the no-cataract group having the lowest scores (less cognitive impairment). For the within-group analysis, at follow-up, the cataract/no surgery group and the cataract/surgery group had significantly less cognitive impairment (P<.001), whereas the no-cataract group experienced no change. For those with cataract, there were no associations between changes in visual function and cognitive function. CONCLUSION: Improvement in cognitive function may occur after cataract surgery but cannot be attributed to the cataract surgery per se or to improved visual function. Clinicians may find this information useful when discussing the nonvisual outcomes of cataract surgery with patients. © 2005 by the American Geriatrics Society.