The proposed study is designed to enhance our ongoing research program on antiretroviral adherence in India. In the first two and a half years of the current study, we have identified culturally-specific adherence patterns and barriers, developed feasible and acceptable adherence measures, and developed reliable and valid scales to examine AIDS-related stigma. We recruited a cohort of private clinic patients on ART, have excellent retention rates (96% at both 6 and 9 months), and developed a working model of ART adherence in this setting. In this proposal, we will continue to build on this work by developing and pilot testing an adherence intervention for private clinic patients. We also propose to address two important new questions that have arisen with the evolution of HIV treatment in India and that may have implications for adherence interventions and treatment guidelines. When this study was first proposed, ART was available on a limited basis in India, and only in the private sector. In 2004, the Indian government began distributing ART, and currently treats about 2/3 of the approximately 70,000 Indian ART patients. Preliminary data suggest that some factors that impact adherence may operate somewhat differently in the public sector. We therefore propose to extend our research to a public clinic setting, to examine the applicability of our working model of adherence and to use these data to modify and pilot test our private clinic intervention in the public health sector as well. Given that only a limited number of first-line ART regimens are available at free or greatly reduced rates in India, as in much of the developing world, prevention of the development of HIV drug resistance is critical to maximizing the efficacy and durability of these regimens and to prevent the transmission of drug resistant virus. However, the longitudinal data needed to accomplish this goal are lacking in the Indian setting, and resistance data only exists on a total of 53 treatment-experienced patients to date. Longitudinal studies examining the development of HIV drug resistance in India are therefore urgently needed and may also have implications for treatment guidelines for other countries affected with HIV subtype C. The current grant has placed our research team in a position to address these critical issues. We have Indian government clearance for our research, an excellent research infrastructure, access to patients in both private and public clinics, and have assembled a team of experts in the fields of adherence, HIV treatment and resistance. We are thus uniquely positioned to quickly implement the first Indian study of the association between adherence patterns, types of regimens and the development of HIV drug resistance and to pilot test the first empirically-based ART adherence intervention in India.