People who recently became infected with HIV often have a high level of the virus and may be highly infectious. If they have sex (especially anal intercourse) without condoms soon after they have been infected with HIV, there is a great chance that they may transmit the virus to others. When they learn of their HIV infection, some but not all men change sexual behaviors so as not to infect their partner(s) with HIV. Possible reasons for such behavior change include increase or decrease in drug use and what is going on within their sexual partnerships. A study that tracks men with recent HIV infection and their partners over time can provide information key to stopping further spread of HIV given that sexual behaviors can vary over time, especially during this most infectious period.