We determined incidence and risk factors for acute and chronic hepatitis B virus (HBV) infection and HBV vaccination rates among human immunodeficiency virus (HIV)–infected subjects from the Adult/Adolescent Spectrum of HIV Disease Project, during 1998–2001. Among 16,248 HIV-infected patients receiving care, the incidence of acute HBV was 12.2 cases/1000 person-years (316 cases), was higher among black subjects (rate ratio [RR], 1.4; 95% confidence interval [CI], 1.0–2.0), subjects with alcoholism (RR, 1.7; 95% CI, 1.2–2.3), subjects who had recently injected drugs (RR, 1.6; 95% CI, 1.1–2.4), and subjects with a history of AIDS-defining conditions (RR, 1.5; 95% CI, 1.2–1.9) and was lower in those taking either antiretroviral therapy (ART) with lamivudine (RR, 0.5; 95% CI, 0.4–0.6), ART without lamivudine (RR, 0.5; 95% CI, 0.3–0.7), or ⩾1 dose of HBV vaccine (14% of subjects) (RR, 0.6; 95% CI, 0.4–0.9). Prevalence of chronic HBV was 7.6% among unvaccinated subjects. HBV rates in this population were much higher than those in the general population, and vaccination levels were low. HBV remains an important cause of comorbidity in HIV-infected persons, but ART and vaccination are associated with decreased disease