The questionnaire design process began by collecting as many instruments and items as we could that had attempted to measure self-reported medication adherence. We first conducted a literature review using combinations of the following search terms: HIV, highly active antiretroviral therapy, medication adherence, self-report, questionnaires, survey methodology. In addition we reviewed references of review articles and directly contacted a number of investigators. There were dozens of such questions that varied in their reference period, how they were worded, what respondents were supposed to report about, and the response tasks respondents were supposed to use to provide answers (a detailed list of the items we considered is available from the first author upon request). We focused our initial attention on the question wording and response tasks that seemed to be used most often and had the strongest face validity.