Antiretroviral therapy (ART) greatly reduces morbidity and mortality for people with HIV/AIDS. However, for optimal effectiveness patients must achieve strict adherence to dosing regimens, which is difficult to maintain over the long term. Interventions to improve adherence have shown promising results, but with small effects. One explanation for small overall effects is that some patient subgroups are less able to benefit from current interventions; however, this explanation lacks empirical support. This study used multilevel modeling of data from a randomized controlled trial in an exploratory analysis to assess whether patient factors moderated the impact of peer support and pager reminders on ART adherence and biological markers of HIV. According to 272 interaction models using an alpha-corrected significance criteria, none of 34 patient characteristics significantly moderated either intervention. Findings suggest that intervention research might more profitably focus on other ways of improving effects, like individual patient needs, rather than target subgroups.