Thirty-three patients with central vein occlusion were evaluated for the effects of scatter xenon arc panretinal photocoagulation. Thirty-four eyes (2 eyes of 1 patient) were randomly divided into a treatment (15 eyes) and a nontreatment group (19 eyes). The average follow-up per eye has been 29 months. The visual prognosis was not significantly better in either group. There was no difference in the development of fundus neovascularisation between groups. None of the patients in the treated group developed rubeosis or neovascular glaucoma. Two patients in the nontreatment group initially had rubeosis and 3 developed it after entry. All 5 involved eyes developed neovascular glaucoma. A significantly greater amount of central retinal capillary drop-out was present in the untreated eyes that developed rubeosis than those untreated eyes which did not. The eyes in the treated group had a similar range of capillary drop-out area, but none of these eyes developed rubeosis or neovascular glaucoma. Panretinal photocoagulation prevented the development of rubeosis and neovascular glaucoma in susceptible eyes.