To the Editor.
—Observational studies and randomized trials both provide important, relevant, and complementary information to the totality of evidence. For antioxidant nutrients and disease, randomized trials, by minimizing the effects of known as well as unknown confounders, provide the most reliable evidence.1 In addition to the National Eye Institute-sponsored age-related eye disease study mentioned by the authors of a recent article2 and Editorial,3 two additional trials of antioxidant vitamins and disease will help to clarify the potentially important public health benefits of vitamin supplementation. The Physicians' Health Study4 and the Women's Health Study5 are ongoing trials of cancer and cardiovascular disease in men and women, respectively, that have also been funded by the National Eye Institute to extend investigation to include age-related macular degeneration and cataract. The Physicians' Health Study is a randomized, double-blind, placebo-controlled trial of aspirin and beta carotene in cardiovascular disease