Since this study is conducted by mail among physicians nationwide, examinations cannot be performed on all patients to determine when they have reached an end point. Reported diagnoses of cataract are confirmed by medical record review. The primary analysis will be of incidence of cataract in the aspirin and placebo groups. In addition, the Cox proportional hazards model will be used to determine whether there is a difference in time to cataract diagnosis between the two groups. It has been postulated that the potent antioxidant properties of beta-carotene might make it effective in preventing cataract development. The investigators will thus determine whether there is a difference in the numbers of cataracts between the beta-carotene/placebo groups and the aspirin/placebo groups.