Objective: To validate and evaluate the reproducibility of a self-efficacy (SE) scale for adherence to antiretroviral therapy in children and adolescents with HIV/AIDS, taking into account the perspective of parents/guardians. Methods: The study was carried out at the Hospital-Dia, Centro de Referência e Treinamento em DST/AIDS (CRT/SP), in São Paulo, Brazil. The parents/guardians of 54 children and adolescents aged 6 months to 20 years were interviewed during routine consultations at our service. Data on SE were collected using the Self-Efficacy for Following Anti-Retroviral Prescription Scale, and SE scores were calculated in two different ways: factor analysis and a predefined formula. The scale's internal consistency was verified using Cronbach's α coefficient. Validity was tested by comparing the mean scores of a group of patients who did adhere to antiretroviral treatment with those of a group that did not (Mann-Whitney test) and by calculating the Spearman correlation coefficient for agreement between scores and clinical parameters. Reproducibility was verified using the Wilcoxon test, intraclass correlation coefficients (ricc) and Bland-Altman plots. Results: The SE scale demonstrated good internal consistency (α = 0.87) and good reproducibility (r icc = 0.69 and r icc = 0.75). In terms of validity, the SE scale was capable of differentiating adherent patients from those who did not adhere to their antiretroviral treatment (p = 0.002) and exhibited a significant correlation with CD4 counts (r = 0.28; p = 0.04). Conclusions: The SE scale can be used to assess adherence to antiretroviral therapy in children and adolescents with HIV/AIDS, taking into account the perspective of parents/carers. Copyright © 2008 by Sociedade Brasileira de Pediatria.8414146Matida, L.H., da Silva, M.H., Tayra, A., Succi, R.C., Gianna, M.C., Gonçalves, A., Prevention of mother-to-child transmission of HIV in São Paulo State, Brazil: An update (2005) AIDS, 19 (SUPPL. 4), pp. S37-S41Gibb, D.M., Goodall, R.L., Giacomet, V., McGee, L., Compagnucci, A., Lyall, H., Paediatric European Network for Treatment of Aids Steering Committee. Adherence to prescribed antiretroviral therapy in human immunodeficiency virus-infected children in the PENTA 5 trial (2003) Pediatr Infect Dis J, 22, pp. 56-62Pluciennik, A.M., (2003) Transmissão materno infantil do vírus da imunodeficiência humana adquirida: Quanto custa não prevenir [tese], , São Paulo: Faculdade de Saúde Pública da USP;Dyke, R.B.V., Lee, S., Johnson, G.M., Wiznia, A., Mohan, K., Stanley, K., Reported adherence as a determinant of response to highly active antiretroviral therapy in children who have human immunodeficiency virus infection (2002) Pediatrics, 109 (4), pp. 1-7Starace, F., Massa, A., Amico, K.R., Fisher, J.D., Adherence to antiretroviral therapy: An empirical test of the information-motivation-behavioral skills model (2006) Health Psychol, 25, pp. 153-162Shah, C.A., Adherence to high activity antiretroviral therapy (HAART) in pediatric patients infected with HIV: Issues and interventions (2007) Indian J Pediatr, 74, pp. 55-60Leite, J.C., Drachler, M.L., Centeno, M.O., Pinheiro, C.A., Silveira, V.L., Desenvolvimento de uma escala de auto-eficácia para adesão ao tratamento anti-retroviral. (2002) Psicol Reflex Crit, 15, pp. 121-133Bandura, A., Self-efficacy: Toward a unifying theory of behavioral change (1977) Psychol Rev, 84, pp. 191-215Gortmaker SL, Lenderking WR, Clark C, Lee S, Fowler MG, Oleske JMThe ACTG 219 Team. Development and use of a pediatric quality of life questionnaire in AIDS clinical trials: reliability and validity of the general health assessment for children. In: Drotar D. Measuring health-related quality of life in children and adolescents: implications for research and practice. Mahwah, NJ: Lawrence Erlbaum Associates1998. p. 219-35Eiser, C., Morse, R., Quality-of-life measures in chronic diseases of childhood (2001) Health Technol Assess, 5, pp. 1-95Streiner, D.L., Norman, G.R., (2003) Health measurement scales: A practical guide to their development and use, , 3rd ed. Oxford: Oxford University Press;Drotar D, Levi R. Critical issues and needs in health-related quality of life assessment of children and adolescents with chronic health condition. In: Drotar D. Measuring health-related quality of life in children and adolescents: implications for research and practice. Mahwah, NJ: Lawrence Erlbaum Associates1998. p. 3-23