A randomized, three-group, prospective, quasi-experimental design was used to evaluate the effectiveness of a theoretically based intervention incorporating a nurse-case-managed approach compared with that of two standard programs on completion of an HAV and HBV vaccination series among sheltered homeless adults in the Skid Row area of Los Angeles. Data were collected from 865 homeless participants at baseline and 6-month follow-up between September 2003 and August 2007. The University of California, Los Angeles, Human Subjects Protection Committee provided oversight of all study activities.