Obstruction of a major temporal branch vein, or one of its macular tributaries, presents a significant threat to vision. Visual acuity may be reduced by macular edema or the consequences of retinal neovascularization, and these afflictions frequently become irreversible. Since the complicating macular edema and retinal neovascularization respond, at least in part, to argon laser therapy in some other conditions, some investigators have begun to treat branch vein occlusions with this modality. However, since the pathogenesis and natural history of the disorder have not yet been elucidated by prospective studies, it is not clear whether such treatment is indicated. Clinical and experimental studies are reviewed, and treatment rationale and techniques are discussed. The authors emphasize the need for well-controlled randomized studies to evaluate the natural history of branch vein occlusion and the efficacy of photocoagulation in its treatment.