In 2002, CDC developed the National HIV Behavioral Surveillance (NHBS) System to help state and local health departments in areas with high AIDS prevalence monitor selected behaviors and assess the use of prevention programs and services in 3 groups at high risk of HIV infection: MSM, IDUs, and heterosexuals. This report summarizes data gathered from May 2005 through February 2006, the first data collec¬tion cycle among IDUs. The report provides descriptive data that serve as a baseline for monitoring trends in risk behaviors and that aid in identifying opportunities to prevent HIV among IDUs.