Sixty-one patients (64 eyes) with central retinal artery occlusion (CRAO) and 41 patients (44 eyes) with branch retinal artery occlusion (BRAO) were studied in detail clinically to find out the pathogenesis of their ocular neovascularization (NV). Ocular NV was seen in 12 eyes (11 patients) with CRAO: iris NV was seen in all 12 eyes, angle NV was seen with neovascular glaucoma (NVG) in ten of them, and no NV was seen in BRAO. Nine of ten patients with CRAO associated with NVG were old, having severe carotid artery disease (CAD) and severe generalized atherosclerotic arterial disease; in the remaining patient, NVG was caused by diabetes mellitus. Severe CAD results in chronic ocular ischemia, which, in turn, produces NV of the iris and angle and NVG; the latter, combined with poor perfusion pressure in the central retinal artery (caused by severe CAD), results in CRAO. Our study showed little evidence that CRAO, per se, is responsible for ocular NV. Various evidence in support of this hypothesis is presented. Our study also showed that the only eyes to recover good vision were those with transient CRAO for up to 11/2 hours, and no treatment helped.