The National Institute of Child Health and Human Development (NICHD) intends to negotiate with and issue a sole source follow-on to an existing contract to Family Health International (FHI) – N01-HFD-0-3301. The follow-on is to extend the observation period of a prospective study of the effect of hormonal contraceptives on the risk of human immunodeficiency virus (HIV) acquisition through heterosexual intercourse. This international study includes long-term follow-up of women who are currently seronegative for HIV, but who live in regions with a high incidence of acquisition of HIV. The study includes research to define the role of hormones on associated factors that may affect HIV acquisition or transmission, such as bacterial vaginosis, Herpes Simplex Virus (HSV), Human Papilloma Virus (HPV) and genital HIV shedding. The academic/international HIV/contraceptive research infrastructure already in place at FHI, under the established contract, makes a competitive offering of this project not feasible. This action is conducted under the authority of 41 U.S.C. 253(1), as set forth in FAR 6.302-1. See numbered Note 22.