This article reviews the major topic areas of compliance research. Much of the research in the area has focused on measurement, extent, and determinants of non-compliance. Research on the effectiveness of educational and behavioural strategies to improve compliance suggests the need to combine them. While some authors have attempted to model compliance or medication-taking behaviours, these models cannot be applied widely. After decades of compliance research, very little consistent information is available, except that people do not take their medications as prescribed. The methodological rigour of compliance studies may partially contribute to this situation. Methodological flaws have included design features and study execution. In addition, researchers have proceeded with studies without regard to a theoretical framework. Many have argued that much of the existing compliance literature also lacks conceptual rigour. Although we know that people do not take their medications consistently, we do not know specifically why they have done so. One reason for this lack of understanding is that compliance research has been dominated by the perspective of the health professional. To better understand medication-taking behaviour, researchers need to examine the patient's perspective. Consequently, future research needs to investigate a patient's decision-making process and the reasons for those decisions.