BACKGROUND: Hepatitis A is the most common type of hepatitis reported in the United States. Prior to hepatitis A vaccine introduction in 1996, hepatitis A incidence followed a cyclic pattern with peak incidence occurring every 10-15 years. During 1980-1995, between 22,000 and 36,000 hepatitis A cases were reported annually. Since 1996, hepatitis A vaccination recommendations have included adults at risk for infection and children living in communities with the highest disease rates. This study provides the first national estimates of self-reported hepatitis A vaccination coverage among persons aged 18-49 years in the United States. METHODS: We analyzed the 2007 National Immunization Survey-Adult (NIS-Adult) data with restrictions to individuals aged 18-49 years. National estimates of hepatitis A vaccination coverage were calculated based on self-report and multivariable logistic regression analysis was used to identify factors independently associated with hepatitis A vaccination status. RESULTS: Among adults aged 18-49 years, 12.1% (95% confidence interval, CI=9.9-14.8%) had received two or more doses of hepatitis A vaccine in 2007. Hepatitis A vaccination coverage was significantly higher among adults aged 18-29 years (15.6%) and adults aged 30-39 years (12.9%) compared with adults aged 40-49 years (8.3%). Coverage was significantly lower for Hispanics (7.1%) compared with non-Hispanic whites (12.5%). Characteristics independently associated with a higher likelihood of hepatitis A vaccination among persons aged 18-49 years included younger age groups, persons at or above poverty level, persons with public medical insurance, and persons who received influenza vaccination in the past season. CONCLUSIONS: In 2007, self-reported hepatitis A vaccination coverage among adults aged 18-49 years was 12.1%. These data provide the first national hepatitis A vaccination coverage estimates among adults and are very important in planning and implementing strategies for increasing hepatitis A vaccination coverage among adults at risk for hepatitis A.