We explored methodological issues related to antiretroviral adherence assessment, using 6 months of data collected in a completed intervention trial involving 136 low-income HIV-positive outpatients in the Bronx, NY. Findings suggest that operationalizing adherence as a continuous (versus dichotomous) variable and averaging adherence estimates over multiple assessment points (versus using only one) explains greater variance in HIV-1 RNA viral load (VL). Self-reported estimates provided during a phone interview accounted for similar variance in VL as EDM estimates (R (2) = .17 phone versus .18 EDM). Self-reported adherence was not associated with a standard social desirability measure, and no difference in the accuracy of self-report adherence was observed for assessment periods of 1-3 days. Self-reported poor adherence was more closely associated with EDM adherence estimates than self-reported moderate and high adherence. On average across assessment points, fewer than 4% of participants who reported taking a dose of an incorrect amount of medication.