This study sought to identify factors influencing HIV testing decisions among clients at a sexually transmitted disease clinic, gay men, and injection drug users. Focus group and intensive interview data were collected from 100 individuals. The AIDS Risk Reduction Model was adapted to describe factors that affect test decisions. Testing barriers and facilitators were grouped as factors affected by "Individual" beliefs, "System" policies and programs, "Testing" technology, and "Counseling" options. Individual factors (fear of death and change), system factors (anonymous test availability, convenience), and counseling and testing factors (rapid results, counseling alternatives) interact to determine whether an individual does not test ("apprehension") or does test ("action"), and ultimately, tests routinely ("integration"). In conclusion, traditional HIV testing presents barriers to some populations at risk for HIV. These findings suggest several strategies to improve HIV test acceptance: acknowledge fears, address system barriers, utilize available test technologies, and expand counseling options.