This paper presents findings of a multi-site study designed to document: (1) caregivers' regimen knowledge; (2) barriers to adherence; and (3) the relationships between adherence, regimen knowledge and barriers. Fifty-one predominantly female, African American parents and caregivers of HIV-infected children completed the Treatment Interview Protocol (TIP), a brief, structured interview designed to assess regimen knowledge and barriers to adherence. TIP data were compared to information obtained from medical records and pharmacy refill histories. Forty-nine per cent of children were considered adherent, defined as > or = 90% refill rate, which was significantly associated with virologic response. Significant regimen knowledge deficits were observed among caregivers, and inaccurate identification of prescribed medications was significantly associated with adherence. Caregivers identified 21 barriers to adherence, and poor adherence was significantly related to the number of barriers reported. Results indicate that the TIP is a successful tool for identifying regimen knowledge, potential adherence barriers and adherence problems. Results suggest that the TIP could be integrated into clinical practice as a quick, effective tool to identify poor adherers and guide interventions and treatment decision making.