 - Identifiable risk behavior for HIV infection, including: sexual partners of HIV positive people, sexual intercourse with a partner of unknown HIV status if that partner is reported to be at higher risk for HIV infection, gay men reporting any unprotected anal intercourse with partners of unknown status in the 12 months preceding study entry, individuals diagnosed with a sexually transmissible infection STI in the 12 months preceding entry that may have been acquired through anal or vaginal intercourse, individuals reporting sharing of injecting equipment in the last 12 months. 