Comparative case studies were used to explore religious congregations' HIV involvement, including types and extent of activities, interaction with external organizations or individuals, and how activities were initiated and have changed over time. The cases included 14 congregations in Los Angeles County representing diverse faith traditions and races-ethnicities. Activities fell into three broad categories: (1) prevention and education; (2) care and support; and (3) awareness and advocacy. Congregations that engaged early in the epidemic focused on care and support while those that became involved later focused on prevention and education. Most congregations interacted with external organizations or individuals to conduct their HIV activities, but promoting abstinence and teaching about condoms were conducted without external involvement. Opportunities exist for congregations to help address a variety of HIV-related needs. However, activities that are mission-congruent, such as providing pastoral care for people with HIV, raising HIV awareness, and promoting HIV testing, appear easier for congregations to undertake than activities aimed at harm reduction.