Purpose: Description of study participants and documentation of the desired diversity in the Prevention Research Centers Healthy Aging Research Network's Workgroup on Promoting Cognitive Health large multisite study designed to examine attitudes about brain health, behaviors associated with its maintenance, and information-receiving preferences among a diverse group of older Americans, to provide a foundation for developing health promotion interventions. Design and Methods: Four hundred fifty older adults in 55 focus groups at 9 sites completed a common participant survey. Using descriptive statistics, the analysis compares participant characteristics (age, sex, and race/ethnicity; rural-urban location; income and education; social activity; physical activity, nutrition, and body mass index; and self-reported measures of cognitive function) across sites and with national data. Results: Comparisons across sites document the rich diversity of the sample. Implications: The substantial representation of a variety of demographic groups suggests that the qualitative data obtained in the focus group research provide a useful basis for developing well-targeted communication interventions for promoting brain health in diverse populations.