In the United States, acute viral hepatitis most frequently is caused by infection with hepatitis A virus (HAV), hepatitis B virus (HBV), or hepatitis C virus (HCV). These unrelated viruses are transmitted through different routes and have different epidemiologic profiles. Safe and effective vaccines have been available for hepatitis B since 1981 and, for hepatitis A, since 1995. Cases in 2005, the most recent for which data are available, are compared with those from previous years. Cases of acute viral hepatitis are reported to CDC via the National Notifiable Diseases Surveillance System. Since 1995, the incidence of reported acute hepatitis A has declined by 88%, to the lowest rate ever recorded (2005: 1.5/100,000 population). Declines were greater among children and in states where routine vaccination of children was recommended beginning in 1999, compared with the remaining states. The proportion of cases among adults has increased. Since 1990, reported acute hepatitis B incidence has declined by 79%, to the lowest rate ever recorded (2005: 1.8/100,000 population). Declines occurred among all age groups but were greatest among children aged <15 years. Since the late 1980s, acute hepatitis C incidence also has declined. In 2005, as in previous years, the majority of these cases occurred among adults, and injection-drug use was the most common risk factor. The greater declines in hepatitis A rates among the states and age groups included in the 1999 recommendations for routine childhood hepatitis A vaccination suggest that this strategy reduced rates. Universal hepatitis B vaccination of children has resulted in substantially lower rates among younger age groups. Higher rates of hepatitis B continue among adults, particularly males aged 25-44 years, which emphasize the need to vaccinate adults at risk for HBV infection. The decline in hepatitis C incidence is primarily attributed to a decrease in incidence among injection-drug users (IDUs). The reasons for this decrease are multifactorial and are probably related to risk-reduction practices among IDUs. The recent expansion of recommendations for routine hepatitis A vaccination to include all children in the United States aged 12-23 months is expected to further reduce hepatitis A rates. Ongoing hepatitis B vaccination programs will ultimately eliminate domestic HBV transmission, and increased vaccination of adults who have risk factors will accelerate progress toward elimination. Prevention of hepatitis C relies on identifying and counseling uninfected persons at risk for hepatitis C (e.g., IDUs) regarding ways to protect themselves from infection.