A population-based study found an overall incidence rate of symptomatic retinal vein occlusion (RVO) in a 4-year period to be 2.14 per 1,000 in the 40 years and over age group. When cases found among glaucoma clinic patients were separated from the remainder of the population there was marked difference in the incidence rate of RVO in the same time period (1.85 and 17.3 per 1,000, respectively). The rate of RVO increased significantly (p less than 0.001) with age in the general population from 0.93 per 1,000 among persons under 64 years of age to 5.36 per 1,000 among persons over 65. The increase in the rate of RVO by age was less dramatic in the glaucoma clinic population. The two populations also differed in the frequency of the occlusion type: the ratio of the rate of branch vein occlusion to central vein occlusion was 3.2:1 in the general population, but equally distributed in the glaucoma clinic population. Persons with increased intraocular pressure and/or glaucoma were found to have a higher prevalence of RVO than persons with no history of elevated intraocular pressure.