From 2000 to 2011, there were 903 and 1,484 incident diagnoses of acute and chronic hepatitis B virus infections, respectively, among active component members of the U.S. Armed Forces; crude overall incidence rates during the period were 5.8 (acute hepatitis B) and 9.5 (chronic hepatitis B) per 100,000 person-years. Incidence rates of both acute and chronic hepatitis B declined during the period. There were relatively high crude rates of hepatitis B diagnoses among service members who were Asian/Pacific Islanders, females, health care workers, and older than 40 years. Declining rates of hepatitis B diagnoses in the U.S. military likely reflect increased avoidance of risky behaviors, vaccination of immunologically naive recruits, and accession into service of increasing numbers of individuals immunized during childhood.