Association of "senile" cataract (SC) with glucose intolerance (impaired tolerance and diabetes) was assessed by sex and age in a random population sample comprising 930 individuals aged 40-70 yr, who underwent concurrent oral glucose tolerance test and ophthalmoscopy. The eye examination was performed without knowledge of the glucose tolerance status. SC was defined as lens opacification preventing visualization of the eyeground or as surgical aphakia due to SC. To assess the independent effect of hyperglycemia, glycosylated hemoglobin (HbA1) was determined in 769 participants. In men, no association was found between SC, glucose intolerance, and HbA1. In women of all ages, glucose intolerance was associated with an SC risk ratio of 6.1 (95% confidence limits 3.3-11.1; P less than 0.001). Furthermore, SC was associated in women with increased HbA1 independently of the effect of glucose intolerance (P less than 0.01). These findings confirm the reported association of SC with diabetes (although unlike the Framingham and HANES population studies, the association was confined in women), indicate its presence at all degrees of glucose intolerance, and suggest a possible independent role of nonenzymatic glycosylation in its pathogenesis.