The prevalence of hepatitis B virus (HBV) in the homeless population is underestimated despite multiple behavioral risks. Data from a sample of 534 homeless adults from downtown Los Angeles were analyzed to examine the prevalence and predictors of HBV infection in this community. The prevalence of HBV was 7 to 10 times higher than in the US general population rate. Opiate dependence, injection and noninjection use, was an independent predictor of HBV exposure. Testing and counseling occurred at significantly lower rates for HBV than for human immunodeficiency virus. Findings emphasize the need to enhance screening and counseling in homeless communities and other populations with opiate use.