OBJECTIVE--To examine the relationships of past and current physical activity to the prevalence of PDR. RESEARCH DESIGN AND METHODS--Individuals diagnosed with diabetes less than 30 yr of age (n = 818), who were participants in the population-based Wisconsin Epidemiologic Study of Diabetic Retinopathy, were examined during 1984-1986. Stereoscopic fundus photographs were graded for presence of PDR. Physical activity was assessed by an interviewer-administered standardized questionnaire. RESULTS--Women diagnosed with diabetes less than 14 yr of age who reported a history of participation in team sports in high school or college were less likely to have PDR at examination (OR 0.46, 95% CI 0.23, 0.93). Those women who reported current strenuous activity levels were less likely to have PDR (OR 0.34, 95% CI 0.13, 0.87). There were no significant associations between past or current physical activity and PDR in men. Current levels of energy expenditure were not related to PDR in either sex. CONCLUSIONS--Higher levels of physical activity may be associated with a reduced risk of having PDR in women. However, the lack of similar findings in men suggests that physical activity may be a relatively unimportant factor in the etiology of PDR.