Objective - To examine prospectively the association between dietary intake of vitamins C and E, carotene, and riboflavin and cataract extraction in women. Design - Prospective cohort study beginning in 1980 with eight years of follow up. Setting - 11 states of the United States. Participants - Female registered nurses who were 45 to 67 years of age. 50,828 women were included in 1980 and others were added as they became 45 years of age. Main outcome measure - Incidence of extraction of senile cataracts. Results - 493 cataracts were extracted during 470,302 person years of follow up. Intake of carotene and vitamin A was inversely associated with cataract: in multivariate analyses, women in the highest fifth of total vitamin A intake (excluding supplements) had a 39% lower risk of cataract relative to women in the lowest fifth (relative risk 0.61; 95% confidence interval 0.45 to 0.81). Neither riboflavin nor dietary vitamins E or C were associated with cataract in a multivariate analysis. Among specific food items spinach (rather than carrots, the greatest source of β carotene) was most consistently associated with a lower relative risk. The risk of cataract was 45% lower among women who used vitamin C supplements for 10 or more years (relative risk 0.55 (0.32 to 0.96)), but no association was noted for multivitamin intake. Conclusion - Dietary carotenoids, although not necessarily β carotene, and long term vitamin C supplementation may decrease the risk of cataracts severe enough to require extraction.