Women in Canada constitute the fastest growing population groups at risk for infection with HIV and AIDS. Women now represent approximately 40% of all AIDS cases worldwide and approximately 20% of cases in Canada. Although the AIDS epidemic has been ongoing for more than 20 years, surprisingly little is known about the differential efficacy and toxicity of various antiretroviral (ARV) drugs in women as compared to men. This gap in knowledge is a result of the initial exclusion of and continued underrepresentation of women in ARV clinical trials. Many studies suggest that HIV-infected women taking ARV treatment (ART) have more adverse events (AEs) than men, especially in relationship to systemic symptoms like diarrhea, as well as organ toxicity, including hepatotoxicity, lactic acidosis, peripheral neuropathy and, notably, lipodystrophy. Currently, the occurrence and management of AEs is the most important issue in the treatment of HIV. Understanding the reasons for the differences of AEs in HIV-infected women is critical and has yet to be evaluated within a large cohort. It is unknown whether these differences relate to hormonal influences, drug metabolism, adherence, fat distribution, body size or other factors. Some small studies have found that drug levels (e.g. Cmin, Cmax, AUC) are higher in women and are associated with increased toxicity. Ultimately, we plan to conduct a randomized clinical trial (RCT) to assess the utility of therapeutic drug monitoring (TDM) and ARV drug dose adjustment on the frequency of AEs in women. Prior to conducting this RCT, it is critical to conduct this study on ARV pharmacokinetics (PK) in women to obtain additional information on ARV drug levels in women and their relation to AEs.