['Public health emergencies heighten several challenges in risk-communication: providing trustworthy sources of information, reaching marginalized populations, and minimizing fear and public confusion. In emergencies, however, information may not diffuse equally among all social groups, and gaps in knowledge may increase. Such knowledge gaps vary by social structure and the size, socioeconomic status, and diversity of the population. This study explores the relationship between risk-communication capabilities, as perceived by public officials participating in emergency tabletop exercises, and community size and diversity.', 'For each of the three communication functions tested, risk-communication capabilities are perceived to be greater in communities with fewer then 10% of the population speaking a language other than English at home, decreasing as the percentage grows to 20% (ANOVA P </= 0.02). With respect to community size, however, we found an N-shaped relationship between perceived risk communication capabilities and population size. Capabilities are perceived highest in the largest communities and lowest in the smallest, but lower in communities with 20,000-49,999 inhabitants compared to those with 2,500-19,999.'] Does risk-communication capability for public health emergencies vary by community diversity?