Background: The burden of HIV/AIDS has not been described for certain rural areas of the United States (Appalachia, the Southeast Region, the Mississippi Delta, and the US-Mexico Border), where barriers to receiving HIV services include rural residence, poverty, unemployment, and lack of education. Methods: We used data from Centers for Disease Control and Prevention (CDC) HIV/AIDS Reporting System to determine the rates of HIV (data from 29 states) and AIDS diagnoses (data from 50 states and the District of Columbia) in 2000 for the 4 regions by demographic and residential (rural and economic indicators of county of residence) characteristics. Results: The rate of HIV diagnoses in 2000 was lower in rural areas (7.3 per 100,000) than in suburban (8.6 per 100,000) or urban areas (22.7 per 100,000). The highest race-adjusted rate was observed for the US-Mexico Border (21.1 per 100,000), followed by the Mississippi Delta (17.3 per 100,000), Southeast Region (14.7 per 100,000), and Appalachia (10.4 per 100,000). Heterosexually acquired HIV was more common in the Southeast Region and the Mississippi Delta than elsewhere. The Mississippi Delta had the highest proportion of HIV diagnoses among young people aged 13-24 years (18.4%). More than three quarters of people diagnosed with HIV in the Mississippi Delta and the Southeast Region were black, and diagnosis rates were higher among blacks and Hispanics than whites in all regions. The distribution of demographic and residential characteristics among people with AIDS was similar to that of all people with a diagnosis of HIV. Conclusion: Strategies are needed to reach the populations of these areas to reduce transmission of HIV.