Intraocular pressure measurements were taken in 2366 diabetic persons and 381 nondiabetic persons who lived in southern Wisconsin. Diabetic persons tended to have higher mean intraocular pressure than the nondiabetic persons. Higher blood pressure, earlier time of day of IOP measurement, absence of cataract and, in some comparisons, female gender, were significantly associated with higher intraocular pressure. In this study rates of a positive history of glaucoma were higher in diabetic persons than in nondiabetic persons and the population participating in the Health Interview Survey. These findings suggest that ophthalmologists must be aware of the increased risk of glaucoma when evaluating diabetic patients.