Abstract : Compliance is defined as the extent to which a patient’s behaviour coincides with medical or health advice. Medication adherence seems to be rather low as 30 to 60 % of patients with chronic disease may be categorised as being poorly or not adherent to drug therapy. Numerous factors may influence compliance among which patient’s characteristics, disease peculiarities, drug treatment modalities, physician’s attitudes and health system organisation. The consequences of non-compliance to drug therapy may not only be harmful for patient’s health, but could also negatively impact the financial cost of public health services. Thus, all efforts should be focused to improve drug compliance, if possible by targeting all causes responsible for poor adherence to medications.