The study estimates HIV incidence in the United States from 2006 to 2009 using improved methods. The estimated number of new HIV infections in 2006 was 48,600 (95% CI: 42,400–54,700), increasing to 56,000 in 2007 (95% CI: 49,100–62,900), then decreasing slightly to 47,800 in 2008 (95% CI: 41,800–53,800) and 48,100 in 2009 (95% CI: 42,200–54,000). Overall, incidence remained relatively stable, but there was a significant 21% increase in incidence among people aged 13–29 years, driven by a 34% increase in young men who have sex with men (MSM). Among young black/African American MSM, incidence increased by 48%. MSM accounted for 61% of new infections in 2009, with heterosexual contact accounting for 27%, injection drug use (IDU) for 9%, and MSM/IDU for 3%. The study highlights the disproportionate impact of HIV on racial and ethnic minorities, particularly MSM. The findings emphasize the need for expanded, improved, and targeted prevention efforts to reduce HIV incidence. The methods used involved stratified extrapolation based on data from 16 states and 2 cities, incorporating multiple imputation, stratification, and extrapolation to account for missing data and heterogeneity in testing behavior. The study also addresses limitations in the data, including potential biases in testing frequency and the use of the BED assay for estimating recency of infection. Overall, the study underscores the importance of continued surveillance and prevention strategies to combat the HIV epidemic in the United States.The study estimates HIV incidence in the United States from 2006 to 2009 using improved methods. The estimated number of new HIV infections in 2006 was 48,600 (95% CI: 42,400–54,700), increasing to 56,000 in 2007 (95% CI: 49,100–62,900), then decreasing slightly to 47,800 in 2008 (95% CI: 41,800–53,800) and 48,100 in 2009 (95% CI: 42,200–54,000). Overall, incidence remained relatively stable, but there was a significant 21% increase in incidence among people aged 13–29 years, driven by a 34% increase in young men who have sex with men (MSM). Among young black/African American MSM, incidence increased by 48%. MSM accounted for 61% of new infections in 2009, with heterosexual contact accounting for 27%, injection drug use (IDU) for 9%, and MSM/IDU for 3%. The study highlights the disproportionate impact of HIV on racial and ethnic minorities, particularly MSM. The findings emphasize the need for expanded, improved, and targeted prevention efforts to reduce HIV incidence. The methods used involved stratified extrapolation based on data from 16 states and 2 cities, incorporating multiple imputation, stratification, and extrapolation to account for missing data and heterogeneity in testing behavior. The study also addresses limitations in the data, including potential biases in testing frequency and the use of the BED assay for estimating recency of infection. Overall, the study underscores the importance of continued surveillance and prevention strategies to combat the HIV epidemic in the United States.