The non-compliance of patients with prescribed treatments is considered as a barrier to effective health care. Non-compliance has implications for the health of patients, effective use of resources and assessments of the clinical efficacy of treatments. Research into non-compliance has increased over the last 30 years. This seems to indicate that it is seen as an important area of concern for all health care professionals. Definitions of non-compliance are problematic, as are methods of assessment of its nature and frequency. Many factors which may account for non-compliance have been proposed, as well as methods to improve compliance. Research into these factors however, mainly based on a positivist epistemology, has failed to provide any conclusive answers to the problem. Sound clinical reasons are suggested as the basis for the increase in interest in non-compliance. It is contended, however, that it is not only these reasons that account for the identification of non-compliance as a problem. Non-compliant behaviour is seen as problematic, because it contravenes professional beliefs, norms and expectations regarding the 'proper' roles of patients and professionals. These have formed the basis of an ideology that views patients as passive recipients of health care. It has led to an inherent tendency to 'blame' the patient and view non-compliance as irrational and deviant. The professional view of non-compliance as irrational, is exemplified in the case of individuals with mental illness, where there are inherent assumptions that non-compliance can be seen primarily as a symptom of illness. This denies the legitimacy of patient choice, and has led to attempts to control compliance via suggested legislative measures. Serious moral and ethical problems arise from such measures, and can be seen as the ultimate legitimization of an ideology of non-compliance. The maintenance of professional power and control is suggested as central to the debates surrounding non-compliance. The ideological assumptions underpinning the concept of non-compliance need questioning, and a re-conceptualization of the roles of patients and professionals is required. This must involve a view of patients as active participators in their own health care. Research based on an interpretative epistemology, aimed at understanding individual action, rather than control, would seem a more appropriate model to pursue.