A retrospective study of 63 patients (64 eyes) with symptomatic branch retinal vein occlusion, 30 men and 33 women, was carried out in this study. The ages of the subjects ranged from 40 to 82 years. Systemic hypertension was present in 41 patients and diabetes mellitus in 19. The occlusion involved the superotemporal vein in 39 eyes, inferotemporal vein in 20, superonasal vein in 2 or macular vein in 3. The site of the occlusion could be examined in detail in 57 eyes, and an arterial overcrossing was involved in 53 of these eyes (93%). This incidence of arterial overcrossing was significantly higher in the branch retinal vein occlusion eyes than in control eyes (P less than 0.05).