Research shows that people in the following categories have a higher risk for HIV infection than the general population: those with past or present intravenous drug abuse; those who received a blood transfusion from 1978 to 1985; men and women who have had unprotected sex with multiple partners; men who have had sex with men after 1975; men and women who have exchanged sex for money or drugs (or who have sex partners who have done so); men or women whose past or present sex partners were HIV-infected, bisexual, or intravenous drug users; and men or women with other sexually transmitted diseases. Research also shows that people who request HIV testing despite reporting none of these risk factors also are at increased risk for HIV infection, probably because they have risk factors that they were not willing to report.