Fifty percent of people living with human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) worldwide are female. In Brazil, for example, 240,000 women are infected with HIV, rates of infection in women have increased over the last two decades, and addressing HIV prevention and treatment for women at risk for, or living with, HIV/AIDS remains a challenge. To better address the needs of women living with HIV in Brazil, the Instituto de Pesquisa Clínica Evandro Chagas - Fundação Oswaldo Cruz (IPEC-FIOCRUZ) HIV Women's Cohort was established in 1996 to study the natural history of women seeking HIV care. This analysis describes the characteristics of women in the cohort who participated in HIV clinical trials between 1999 and 2008.