Background. Antiretroviral scale-up is increasing in resource-constrained settings. To date, few studies have explored the barriers and facilitators of adherence to ART in these settings. Facilitators and barriers of antiretroviral adherence in Peru are not completely understood. Methods. At two clinics that serve a large number of HIV-positive individuals in Lima, Peru, 31 in-depth interviews were carried out in 2006 with adult HIV-positive individuals receiving ART. Purposive sampling was used to recruit the participants. Interviews were transcribed and coded using two Spanish-speaking researchers and a content analysis approach to identify themes in the data. Results. Among the participants, 28/31 (90%) were male, 25/31 (81%) were self-identified as mestizo, and 19/31 (61%) had an education above high school. The most frequently discussed barriers to adherence included side effects, simply forgetting, inconvenience, dietary requirements, being away from home, and fear of disclosure/stigma. The most frequently discussed facilitators to adherence included having a fixed routine, understanding the need for compliance, seeing positive results, treatment knowledge, and faith in treatment. Conclusions. Overall, these findings were similar to the facilitators and challenges experienced by individuals on ART in other resource constrained settings. Further treatment support tools and networks should be developed to decrease the challenges of ART adherence for HIV-positive individuals in Lima, Peru.