Few population-based studies in the United States have reported on cataractprevalence and, thus, the inclusion of data from the Rotterdam Study, Rotterdam,the Netherlands; Blue Mountains Eye Study, Sydney, New South Wales, Australia;and the Melbourne Visual Impairment Project, Melbourne, Victoria, Australia,increased the power of our report, thus, allowing narrower confidence limitsin our estimates, especially for the small, but important, population of thevery old. Estimates for white Americans aged 40 through 64 years would otherwisehave been derived from a single report (Beaver Dam Eye Study, Beaver Dam,Wis). Most Australians immigrated originally from the same European countriesfrom which white Americans came (notably England, Ireland, Scotland, Germany,Italy, and Greece). Still, there are various factors that might lead to differencesin cataract prevalence between countries. These include latitude (as a surrogatefor exposure to cataractogenic UV-B light),17 differentialrates of cataract surgery, and possible cultural differences with regard todiet, tobacco smoking, and alcohol use. However, our study did not find systematicdifferences between European, Australian, and US studies for the prevalenceof cataract or of pseudophakia/aphakia. The generally similar rates acrossdiverse studies of white persons indicate that pooling is appropriate andsuggest that the estimates are likely to be reliable.