Carolina Dagli-Hernandez,1 Rosa Camila Lucchetta,1 Tales Rubens de Nadai,2 José Carlos Fernandez Galduróz,3 Patricia de Carvalho Mastroianni1 1Department of Drugs and Medications, School of Pharmaceutical Sciences of the UNESP – Univ Estadual Paulista, Araraquara, 2Department of Surgery and Anatomy, Americo Brasiliense State Hospital, 3Department of Psychobiology, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil Objectives: To evaluate which indirect method for assessing adherence best reflects highly active antiretroviral therapy (HAART) effectiveness and the factors related to adherence. Method: This descriptive, cross-sectional study was performed in 2012 at a reference center of the state of São Paulo. Self-report (simplified medication adherence questionnaire [SMAQ]) and drug refill parameters were compared to the viral load (clinical parameter of the effectiveness of pharmacotherapy [EP]) to evaluate the EP. The “Cuestionario para la Evaluación de la Adhesión al Tratamiento Antiretroviral” (CEAT-VIH) was used to evaluate factors related to adherence and the EP and, complementarily, patient self-perception of adherence was compared to the clinical parameter of the EP. Results: Seventy-five patients were interviewed, 60 of whom were considered as adherent from the clinical parameter of the EP and ten were considered as adherent from all parameters. Patient self-perception about adherence was the instrument that best reflected the EP when compared to the standardized self-report questionnaire (SMAQ) and drug refill parameter. The level of education and the level of knowledge on HAART were positively correlated to the EP. Forgetfulness, alcohol use, and lack of knowledge about the medications were the factors most frequently reported as a cause of nonadherence. Conclusion: A new parameter of patient self-perception of adherence, which is a noninvasive, inexpensive instrument, could be applied and assessed as easily as self-report (SMAQ) during monthly drug refill, since it allows monitoring adherence through pharmaceutical assistance. Therefore, patient adherence to HAART could be evaluated using self-perception (CEAT-VIH) and the viral load test. Keywords: health literacy, anti-HIV agents, patient compliance, antiretroviral therapy, highly active, acquired immunodeficiency syndrome