Background: Previous studies have suggested that African-American populations have a lower prevalence of Parkinson's disease (PD); however, because African-Americans are underrepresented in many cohorts, this relationship is poorly understood. We evaluated data from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study to describe potential racial differences in PD prevalence. Methods: We identified subjects using PD medications from the REGARDS study, a national longitudinal cohort study of 30,000 persons over age 45 with approximately equal representation of African-Americans and Whites. Results: The prevalence of PD medication use across the cohort was 0.78% and was less among African-Americans (0.51%) than among Whites (0.97%; OR 1.90; 95% CI 1.31-2.74). There was an association of gender and PD medication use, with a prevalence of 0.61% in females and 0.97% in males (OR 1.57; 95% CI 1.13-2.18). There was no association with income, education level or geographic region of residence. Conclusions: The lower rate of PD medication use among African-Americans supports the suspected lower prevalence of PD among African-Americans suggested by other studies. While racial differences in PD diagnosis and treatment may contribute to the differences we observed, comparable disparities have not been observed in the REGARDS cohort for other diagnoses. Further studies of the REGARDS cohort may lead to important insights into potential biological differences in PD among African-Americans and Whites. Copyright © 2009 S. Karger AG, Basel.