Invite applications for highly focused basic research integrated with the Women's Interagency HIV Study (WIHS) scope and structure. Applications are expected to utilize the WIHS study population, a large cohort of HIV-infected women in the U.S., to formulate specific hypotheses concerning HIV/AIDS pathogenesis in women. The WIHS cohort is followed in five large metropolitan areas (New York, Washington DC, Chicago, Los Angeles and San Francisco).