The results of seven population-based studies were examined separately and pooled to obtain age- and sex-specific estimates of the prevalence of PD. An in-person screening instrument and diagnostic clinical examination were used to detect potential PD cases. The overall prevalence (per 100 population) in persons 65 years of age and older was 1.8, with an increase from 0.6 for those age 65 to 69 years to 2.6 for those 85 to 89 years. There were no sex differences in prevalence of PD.