Adherence is integral to improving and maintaining the health and quality of life of people living with HIV. Two-hundred HIV-positive adults recruited from teaching hospitals and non-governmental organizations (NGOs) in Rio de Janeiro City were assessed on socio-demographic factors, adherence to antiretroviral therapy (ART) and psychosocial factors hypothesized to be associated with ART. Predictors of non-adherence were analyzed using bivariate and multivariate analyses. Self-reported medication adherence was high (82% had adherence >90%). Non-adherence was associated with personal factors (i.e. sexual orientation, self-efficacy), physical factors (i.e. loss of appetite) and interpersonal factors (i.e. doctor-patient relationship). Adherence in Brazil is as good, if not better, than that seen in the US and western Europe, which is noteworthy since the sample was derived predominantly from public healthcare settings. It is possible that the connection to NGOs in Rio de Janeiro City played a helpful role in achieving high levels of adherence in this sample of people living with HIV and AIDS. Recommendations, based on study findings, include enhancing and sustaining supportive services for NGOs, promoting patient self-efficacy and behavioral skills for adherence, increasing social network support and having healthcare providers directly address patients' medication beliefs, attitudes and experience with side effects.