Men who have sex with men (MSM) bear a disproportionate burden of hepatitis B virus (HBV) infections. We used serologic data from the National HIV Behavioral Surveillance (NHBS) system to determine the prevalence and correlates of HBV infection, immunization, and susceptibility in a sample of Los Angeles County MSM. Approximately 19 % (95 % CI 15-24 %) had serologic evidence of current or past infection, while 35 % (95 % CI 30-40 %) were susceptible. Compared with the youngest age group, MSM ages 40-49 years had a lower prevalence of immunization (aPR 0.28, 95 % CI 0.17-0.45) and a higher prevalence of infection (aPR 8.53, 95 % CI 3.95-18.4) and susceptibility (aPR 2.02, 95 % CI 1.13-3.63). We also observed poor concordance between self-reported and serologic measures of vaccination. Our results indicate the possibility of missed opportunities to vaccinate MSM. Gaps in implementing existing vaccination strategies must be addressed to increase hepatitis B vaccination coverage for MSM, especially in older age groups.