Settings with limited health care workers are challenging environments for delivery of antiretroviral therapy. One strategy to address this human resource crisis is to task shift through training selected patients as peer health workers (PHWs) to provide care to other individuals receiving antiretroviral therapy. To better understand processes of a cluster-randomized trial on the effect of these PHWs on AIDS care, we conducted a mixed methods operations research evaluation. Qualitative methods involved patients, PHWs, and clinic staff and included 38 in-depth interviews, 8 focus group discussions, and 11 direct observations. Quantitative methods included staff surveys, process, and virologic data analyses. Results showed that task shifting to PHWs positively affected structural and programmatic functions of care delivery--improving clinical organization, medical care access, and patient-provider communication--with little evidence for problems with confidentiality and inadvertent disclosure. Additionally, this evaluation elucidated trial processes including evidence for direct and indirect control arm contamination and evidence for mitigation of antiretroviral treatment fatigue by PHWs. Our results support the use of PHWs to complement conventional clinical staff in delivering AIDS care in low-resource settings and highlight how mixed methods operations research evaluations can provide important insights into community-based trials.