The mortality experience of patients enrolled in the Diabetic Retinopathy Study is compared with that observed in other prospective studies of patients with diabetic retinopathy, as well as those in other clinical trial populations such as the University Group Diabetes Program and the Coronary Drug Project. Patients were eligible to participate in the Diabetic Retinopathy Study if they had proliferative retinopathy in at least one eye or severe nonproliferative retinopathy in each eye, and had visual acuity of 20/100 or better in each eye and had not had previous photocoagulation treatment. Of the 1,742 patients enrolled either in the argon or xenon treatment group, 409 died. The 1-yr and 5-yr cumulative mortality rates were 3.0 and 22.6, respectively. The mortality rates observed for patients with different levels of severity of retinopathy and baseline abnormalities are examined by type of diabetes. The mortality experience of patients with severe visual loss is also presented.