The primary aim of this study is to compare the effect of an individualized adherence intervention (TI) and a structured adherence intervention (TS) to usual care on adherence to antiretroviral therapy in persons infected with HIV (PWHIV). The secondary aims address the relationship between adherence and quality of life (QOL), and between adherence and clinical response. The exploratory aims focus on examining the effect of self-efficacy on the relationship between the intervention and adherence, the effect of adherence on the relationship between self-efficacy and outcomes (clinical response and quality of life), as well as the effects of symptoms, alcohol and/or drug use, chronic interpersonal problems, mood, social support, optimism, perceived burden of medication regimen, perceived stigma, purpose in life, co-morbidity, personality, literacy, and intimate partner abuse on self-efficacy, and psychometric analyses of the instruments. The sample of 300 (plus 51 dropouts) PWHIV who are taking antiretroviral therapy and without cognitive dysfunction will be randomly assigned to one of two treatment arms. Those individuals who are deemed to be 100% adherers (approximately 25-50) will be assigned to the control group, but will be followed separately as a natural history substudy and interviewed. Data will be collected at baseline, post-treatment, post-maintenance, post-booster, and 18 months. Electronic event monitors, diaries, the Self-reported Medication-taking Scale, and the ACTG Adherence Follow-up Questionnaire will be used to assess adherence. The Digit Vigilance Test will be used to assess the effect of sustained attention on adherence. QOL will be measured using the MOS-HIV, the Satisfaction with Life Scale, and the Perception of Illness Visual Analogue Scale. Clinical response will be assessed using viral load, CD4 T-cell count, AIDS defining conditions, and hospitalizations. Variables influencing self-efficacy (measured with an investigator-developed Self-efficacy Scale) will be examined: symptoms ( CRCD Symptom Checklist), alcohol and/or drug use (AUDIT), chronic interpersonal problems (IIP), social support (Interpersonal Support Evaluation List), optimism (Life Orientation Test), anxiety (Beck Anxiety Inventory) and Beck Depression Inventory II), perceived burden of regimen (visual analog scales), perceived stigma (Perceived Stigma of HIV Scale), purpose in life (Purpose in Life Scale), co-morbidity (CRCD Co-Morbidity Scale), personality characteristics (NEO-FFI), health literacy (Test of Functional Health Literacy in Adults), knowledge about HIV medication adherence (HIV Medication Adherence Knowledge), and intimate partner abuse (Abuse Assessment Screen). A repeated measures model with planned comparisons will be used to test the hypotheses for the primary aim. Structural equation modeling will be used to examine the relationships identified in the secondary and exploratory aims. PWHIV who adhere to their therapy may live longer, require fewer hospitalizations, and have an improved QOL.