Virus present in semen likely contributes substantially to the sexual transmission of HIV. However, the source of HIV in semen is unknown. Some evidence suggests that the prostate may be the source of at least some of the virus in semen. This study is designed to determine whether the prostate may serve as the source of virus in semen by comparing the concentration of HIV-1 RNA in semen donated normally, in semen obtained following prostatic massage, and in expressed prostatic secretions. Finding a source for semen HIV would provide important insights into several aspects of HIV sexual transmission. Since some drugs do not enter the prostate well, the finding that virus is produced in the prostate might suggest the prostate could serve as a reservoir for HIV, leading to the development of resistance to antiviral agents.