• The relationship between biochemical markers of antioxidant status and senile cataract was examined in 112 subjects aged 40 to 70 years. Seventy-seven of these subjects had a cataract in at least one lens. Antioxidant status was measured using erythrocyte superoxide dismutase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase activity, and indexes that included these enzymes plus plasma levels of vitamin E, vitamin C, and carotenoids. Subjects were grouped by level (low, moderate, or high) of the enzymes and antioxidant indexes. Results suggest that subjects with high levels of at least two of the three vitamins (vitamin E, vitamin C, or carotenoids) are at reduced risk of cataract relative to subjects with low levels of one or more of these vitamins (odds ratio, 0.2). The erythrocyte enzymes, either individually or in combination, did not appear to differ between subjects with and without cataract.