ARV drug adherence is well recognized to be one of the key determinants of the success of therapy ¹³. Poor adherence can lead to virological failure, the evolution of drug resistance and subsequent immunological and clinical failure ^{90, 189-209}. Adherence is promoted by simplified, well-tolerated regimens involving as few pills as possible administered no more than two times a day. It is important to counsel patients carefully in advance of initiating therapy; this typically involves a coordinated effort by physicians, nurses and other health care providers. ART should not be started at the first clinic visit. It is important to have a period of education and preparation aimed at maximizing adherence. Once treatment has begun, continued monitoring of adherence is essential. In the developed world it has been difficult to define a simple effective method of adherence monitoring for all settings. Assessment by physicians has repeatedly proved to be the least reliable approach. Pill counts are quantitatively useful but are subject to error and manipulation. Validated patient questionnaires have proved one of the more reliable, easily instituted tools for monitoring adherence in the outpatient setting ^{210, 211}.

No single tool, however, can be applicable in all regions and cultures, so each country and/or centre should develop a brief, culturally appropriate patient questionnaire for assessing and monitoring adherence. In some settings, sites may wish to try to introduce directly observed therapy (DOT) with carers’ or family members’ assistance. In particular, sites with tuberculosis treatment programmes may wish to consider this, although the open-ended nature of ART, as opposed to the limited course of treatment for tuberculosis, raises questions about the sustainability of such an approach. Innovative models such as the use of DOT during an initial training period for patients should be evaluated. However, ongoing attention to and reinforcement of adherence throughout the entire course of ART comprise an essential part of any successful treatment programme and should be built into country-specific programmes.