Worldwide, the rate of new HIV infections continues to increase among women. Over the past 5 years there has been a growing focus on the clinical aspects of HIV infection among women. Historically, the majority of subjects enrolled in HIV clinical trials were male patients. Consequently, most knowledge about antiretroviral efficacy and toxicity has been derived from studies of predominately male subjects. More recently, results from clinical trials, especially those that have focused on HIV-infected female subjects, suggest that there may be clinically important gender-related differences in several aspects of HIV disease. These include, but are not limited to, differences in natural history, efficacy and safety of drug treatment. This chapter reviews current data on gender differences in antiretroviral pharmacokinetics and toxicity.