If the theoretical advantages of krypton laser over argon laser are proven clinically, this modality will be an important adjunct in the management of many of the leading causes of blindness. Our preliminary observations in over 400 cases treated with krypton laser correlate well with the theoretical and histopathologic observations of others. Possible advantages of krypton laser therapy for choroidal neovascularization (CNV) include its ability to penetrate foveal xanthophyll and retinal blood vessels and to minimize damage to the nerve fiber layer. Krypton also penetrates the xanthochrome in nuclear sclerotic cataract. The major disadvantage is increased choroidal hemorrhage. In proliferative retinopathies krypton penetrates moderate vitreous hemorrhage. It may minimize both epiretinal membrane changes and continuation of vitreo-retinal traction. It can be used after fluorescein injection. Disadvantages include increased choroidal hemorrhage and increased pain, often requiring retrobulbar anesthesia. Krypton laser cannot close surface neovascularization or stop bleeding by photocoagulating its source. The role of argon laser in CNV or how it benefits proliferative retinopathies is still not understood. The Macular Photocoagulation Study will help define the role of argon and krypton laser for CNV. A similar clinical trial to compare the efficacy of krypton laser to the proven efficacy of argon laser in the treatment of proliferative diabetic retinopathy is still anticipated.