To derive the clinical benefits of antiretroviral (ARV) therapy, HIV+ patients must attain high levels of adherence (90-95 percent). Our work with HIV/AIDS patients has indicated that errors in daily ARV dosing may occur because patients did not understand their dosing instructions. Therefore, if patients are not able to understand medication instructions at the outset of treatment, then they cannot be expected to accurately follow those regimens over time. Functional health literacy refers to the ability to read and comprehend prescription bottles, appointment slips and other materials that ensure successful functioning in the patient role (prose literacy). It also includes using mathematical skills to plan the number and timing of doses each day/week and to anticipate refills (quantitative literacy). Although low prose literacy, age and education have been associated with poor understanding of ARV dosing instructions in HIV/AIDS patients, the role of quantitative literacy has been largely unstudied in this population. Furthermore, cognitive impairment is known to occur as HIV disease progresses and deficits in executive functions (i.e., problem-solving and reasoning) and learning/memory have been linked to failure to comprehend ARV regimen instructions. No studies on the effects of literacy on ARV regimen comprehension to date have accounted for cognitive impairment. Because a substantial proportion of HIV infected patients are likely to be cognitively impaired, the influence of such impairment on understanding of ARV medication regimens must be considered. The proposed cross-sectional study will assess the relation of low prose literacy, low quantitative literacy and deficits in specific neurocognitive ability domains to poor comprehension of ARV regimen instructions in a mostly ethnic minority sample of 200 ARV naTve HIV+ men and women. Initial comprehension of ARV regimens is essential for continued adherence. Identification of factors related to poor comprehension of ARV medication instructions is a necessary prerequisite for developing interventions to improve it.