The purpose of this paper is to describe electronic monitoring device (EMD) (e.g., MEMS caps) use among HIV-infected adults enrolled in a randomized clinical trial and to make explicit some of the benefits and caveats of using electronic monitoring device technology. This is a descriptive, exploratory study of EMD use among 128 HIV-infected adults treated with at least three antiretroviral agents. Thirty-six percent of the sample admitted that they did not use the EMD consistently. Forty-one percent of the subjects reported taking out more than one dose at a time and 26% reported opening the EMD but not taking the medication. Special subject-related issues accounted for only a small percentage of all reported problems with EMD use (e.g., transient housing, incarceration, substance abuse relapse and drug treatment). Results of this study suggest that EMDs may underestimate antiretroviral adherence among HIV-infected adults. Recommendations for improving EMD data quality are presented.