NHANES surveys are cross-sectional surveys designed to compile nationally representative statistics on the health of the U.S. civilian, noninstitutionalized population through complex, multistage probability sampling. During NHANES 2005-2008, a total of 8,283 persons aged 14-49 years were interviewed. Of these, 8,002 had a medical examination; sera were collected from 7,293 participants (88% of those interviewed) for testing of HSV-2 antibodies using a type-specific immunodot assay. Seroprevalence was analyzed by sex, age group, number of lifetime sex partners, and three racial/ethnic categories (non-Hispanic white, non-Hispanic black, and Mexican American). Participants also were asked, “Has a doctor or other health-care professional ever told you that you had genital herpes?” Statistical software was used to generate seroprevalence estimates and 95% confidence intervals. All seroprevalence estimates were weighted using medical examination weights of the survey to represent the U.S. civilian, noninstitutionalized population, accounting for survey participants' unequal probabilities of selection and adjustments for nonresponse. Differences in seroprevalence among categories of participants (e.g., sex or age group) were assessed using the Wald chi-square test.