OBJECTIVE: To summarize the prevalence of retinal vein occlusion (RVO) from studies in the United States, Europe, Asia, and Australia. DESIGN: Pooled analysis using individual population-based data. PARTICIPANTS: Individual participant data from population-based studies around the world that had ascertained RVO from fundus photographs. METHODS: Each study provided data on branch RVO and central RVO by age, sex, and ethnicity. Prevalence rates were directly age and sex standardized to the 2008 world population aged 30 years and older. Estimates were calculated by study and, after pooling, by ethnicity. Summary estimates included studies in which RVO was assessed from fundus photographs on >or=2 fields of both eyes. MAIN OUTCOME MEASURES: Any RVO, CRVO, or BRVO. RESULTS: The combined pooled data contained 68,751 individuals from 15 studies, with participants' ages ranging from 30 to 101 years. In analyses of 11 studies that assessed >or=2 fundus fields of both eyes (n=49,869), the age- and sex-standardized prevalence was 5.20 per 1000 (confidence interval [CI], 4.40-5.99) for any RVO, 4.42 per 1000 (CI, 3.65-5.19) for BRVO, and 0.80 per 1000 (CI, 0.61-0.99) for CRVO. Prevalence varied by race/ethnicity and increased with age, but did not differ by gender. The age- and sex-standardized prevalence of any RVO was 3.7 per 1000 (CI, 2.8-4.6) in whites (5 studies), 3.9 per 1000 (CI, 1.8-6.0) in blacks (1 study), 5.7 per 1000 (CI, 4.5-6.8) in Asians (6 studies), and 6.9 per 1000 (CI, 5.7-8.3) in Hispanics (3 studies). Prevalence for CRVO was lower than BRVO in all ethnic populations. On the basis of these data, an estimated 16.4 million (CI, 13.9-18.9) adults are affected by RVO, with 2.5 million (CI, 1.9-3.1) affected by CRVO and 13.9 million (CI, 11.5-16.4) affected by BRVO. Study limitations include non-uniform sampling frames in identifying study participants and in acquisition and grading of RVO data. CONCLUSIONS: Our study provides summary data on the prevalence of RVO and suggests that approximately 16 million people may have this condition. Research on preventive and treatment strategies for this sight-threatening eye disease is needed.