Eyes with three or four diabetic retinopathy risk factors received laser panretinal photocoagulation with random selection of either blue-green argon (42 eyes) or red krypton (40 eyes) laser to determine if one laser was superior to the other. After 6 months, visual acuity preservation or improvement was obtained in 33 (79%) argon- and 34 (84%) krypton-treated eyes. Peripheral IV-4e visual field constriction of 7% occurred with argon and 10% with krypton. Vitreous hemorrhaging after treatment occurred in 1 argon- and in 6 krypton-treated eyes. Complete disc neovascular regression was obtained in 27 (67%) of 40 argon- and 19 (56%) of 34 krypton-treated eyes, with partial regression occurring in 8 (20%) argon- and 8 (24%) krypton-treated eyes. The two treatments produced essentially equal results.