HIV/AIDS continues to be a major public health problem throughout the world. In 2011, 23.5 million people were living with HIV/AIDS worldwide, with the greatest burden of disease in Africa, representing 2/3 of the total HIV/AIDS population. Specifically, sub-Saharan Africa bears the highest burden of the disease, with 22.9 million people living with HIV/AIDS (PLWHA), 60% of the total infections worldwide. Furthermore, within this region, women are disproportionately affected, accounting for 58% of people living with HIV/AIDS.1 With the continued high prevalence and incidence of HIV among women, despite an increase in prevention interventions, including pre-exposure prophylaxis (PrEP), suggests behavior change still plays a key role in transmission. This dissertation aims to seek to understand high-risk sexual behaviors and other factors associated with an increased risk of secondary transmission among women in order to inform the implementation of new HIV prevention strategies and reduce the burden of HV. Chapter 1 is a brief introduction into HIV and the high-risk sexual behaviors that affect its transmission. Chapter 2 is based on data from a cohort study of recently sero-converted women from the Microbicide Trials Network (MTN) and demonstrated that depression plays a significant role in the acquisition of STIs. Chapter 3 is based on data from a cohort study of recently sero-converted women from the MTN and demonstrated that there are several factors that influence disclosure and timing of disclosure of HIV status. Chapter 4 is based on data from a cohort study of recently sero-converted women from the MTN and demonstrated that high-risk sexual behaviors are still frequent among HIV-infected women, and that ART may modify the risk of high-risk sexual behaviors. Finally, Chapter 5 is a brief discussion of results as well as their implications for future research.