Compliance: The extent to which the participants in a clinical trial follow trial protocol, for instance, following both the intervention regimen and trial procedures (clinical visits, laboratory procedures and filling out the forms). For the clinical trial investigators it is an inescapable fact of life that the participants in their trials many times make life difficult by missing appointments, forgetting to take the prescribed treatment from time to time, or not taking it at all but faking to do so. Because poor participant compliance can harmfully affect the outcome of a trial, it is essential to use methods both to improve and monitor the level of the compliance.