This application addresses the broad challenge area of (06) Enabling Technology and the specific challenge topic 06-OD(OBSSR)-101 Using new technologies to improve treatment adherence. Strict adherence to antiretroviral medications is necessary for people living with HIV/AIDS to achieve sufficient viral suppression to slow disease and alcohol use is a known barrier to medication adherence. Alcohol intoxication effects memory, attention, and other basic cognitive functions that are obviously linked to missing medications. In addition, drinking can affect adherence the day after intoxication due to hangover impairments. Less is known about how alcohol-related beliefs interrupt treatment, such as when individuals believe that they should stop taking their medications to avoid mixing them with alcohol. Believing that mixing alcohol with medications leads to adverse reactions (interactive toxicity beliefs) can result in patients deliberately stopping their HIV therapy. Thus, HIV positive individuals who drink may experience prolonged and dangerous treatment interruptions due to their beliefs about alcohol. There are few studies of alcohol expectancies, including interactive toxicity beliefs, in relation to medication adherence. We propose a 12- month prospective cohort study to examine interactive toxicity beliefs in relation to HIV treatment adherence. Our model predicts that quantity and frequency of alcohol intake will be associated with non- adherence to HIV treatments. We also predict that drinkers who believe that mixing alcohol and HIV medications is toxic will interrupt their therapy when drinking. We hypothesize that interactive toxicity beliefs will predict non-adherence to treatment over and above common factors associated with non- adherence, including quantity and frequency of alcohol consumption. The study will include an innovative combination of reliable and valid technologies for objectively monitoring HIV treatment adherence and alcohol consumption. A cohort of 200 men and women who are (a) taking HIV medications and (b) report drinking alcohol in the previous month will be enrolled in a 12-month prospective cohort. Participant's alcohol and other drug use as well as HIV treatment adherence will be monitored using cell-phone-based assessment technologies. To monitor HIV treatment adherence, we will use unannounced pill counts conducted every 3 to 4 weeks. Alcohol and other drug use will be monitored using daily interactive voice response technology. Multilevel modeling will test a model of interactive toxicity beliefs in relation to alcohol use and medication adherence over a one year period. Our findings will inform interventions to address alcohol use and HIV treatment adherence in HIV/AIDS patients who drink. The benefits of HIV treatment are only realized with persistent strict adherence and alcohol is a known barrier to medication adherence. Alcohol intoxication effects memory, attention, and other basic cognitive functions that obviously lead to missing medication doses. In addition, beliefs that mixing alcohol with medications will result in adverse reactions (interactive toxicity beliefs) may cause particularly hazardous prolonged interruptions in HIV treatment. Beliefs about alcohol and HIV treatments may contribute to the development and spread of treatment resistant virus representing a significant threat to public health as well as personal health.