The provision of ophthalmologic care to diabetic patients was examined in a large, geographically defined population-based study in southern Wisconsin. Of the total of 2,272 patients examined, 902 were taking insulin and were diagnosed before 30 years of age (younger onset) and 1,370 were diagnosed at or after 30 years of age (older onset). Approximately 26% of the younger-onset and 36% of the older-onset diabetic population had never had an ophthalmologic examination. Characteristics of the younger-onset and older-onset population associated with never having had an ophthalmologic examination included living in a nonmetropolitan county, being older at the time of diagnosis, having a shorter duration of diabetes, having fewer years of education, receiving their diabetes care from a family or general practitioner, and having better visual acuity. Eleven percent of younger- and 7% of older-onset persons with Diabetic Retinopathy Study high-risk characteristics for severe visual loss had never been seen or were seen more than two years before the time of the study. Because severe visual loss caused by proliferative diabetic retinopathy may be reduced by timely photocoagulation treatment, this study suggests that a large number of patients who would benefit from ophthalmologic care are currently not receiving it.