India is a nation of contrasts. The economy is modernizing, but the culture is traditional. Different provinces experience the HIV epidemic differently; even in high-prevalence areas, the epidemic reflects diverse social, cultural, religious, & sexual practices. This proposal focuses on 2 high prevalence provinces. As the antiretroviral (ART) program is scaled up, adherence is a key issue that needs to be addressed (as it is a key determinant of resistance, which has public health consequences). With limited affordable second-line regimens & restricted laboratory monitoring in low-income settings, optimal adherence to first-line regimens is essential. The study is a randomized controlled trial of an approach using a contextually relevant intervention (mobile telephones) to influence ART adherence in 600 ART naïve, HIV+ Indian patients eligible for ART, in Karnataka and Tamil Nadu. The conventional existing approach (as in the national guidelines) will be compared with an intervention in which the patient is provided adherence support using a mobile telephone interface. The study besides assessing the effect of intervention on adherence, will also provide data on the proportion of Indian patients failing first line ART. A study of factors associated with adherence, hitherto unstudied in India will be done. In addition the incidence and manifestations of opportunistic infections, immune reconstitution syndrome & adverse drug events will be described. The use of validated low-cost tests that optimize monitoring, are necessary here. Viral load is rarely used to monitor treatment because it is expensive. Instead falling CD4 counts are used. This usually occurs months/years after virological failure (increasing load); patients could have accumulated enough resistant mutations in this time to render other drugs useless. Using an affordable load test (evaluated in this study) will allow earlier detection of failure in this setting, thus having public health implications. Cost effectiveness will be studied. The project has policy implications for India and other low income settings.