Using simple random selection of sites stratified by type (homeless shelter, residential drug treatment recovery sites, or outdoor locations), homeless adults were recruited from 12 homeless shelters, four residential drug treatment recovery sites, and outdoor locations. Eligibility requirements included the following: (a) adult age 18–65 years and designated as homeless; (b) willing to undergo HAV, HBV, HCV, and HIV antibody testing at baseline and at 6-month follow-up; (c) willing to participate in the intervention; and (d) no history of HBV vaccination. As completing the HAV/HBV vaccine series was the key study outcome, persons testing positive for HBV antibodies were excluded from the study. A homeless person was one who had slept in one of the study sites or in the outdoors during the previous night.