Compliance is defined as the extent to which a patient's behaviour coincides with medical or health advice. Medication compliance seems to be rather low as 30 to 60% of no or poor adherence to medical recommendation have been reported. Numerous factors may influence medication compliance among which patient's characteristics, disease particularities, drug treatment modalities or physician's attitudes. The consequences of medication non-compliance may not only be dangerous for patient's health, but also dramatically increase the financial cost for public health services. Thus, all energies should be devoted to improve drug compliance, including treatment optimization and simplification, patient's information and education, use of practical means that facilitate adherence to medical recommendation, the patient being responsible for his/her treatment.