Blood pressure control remains unsatisfactory in all countries of the world with at best 60% of treated hypertensive patients reaching recommended therapeutic goals. Several factors have been identified which may explain why the rate of blood pressure control remains low. Among them, one can cite medical inertia and a poor adherence to drug therapies. In the absence of new drugs to control blood pressure, drug adherence has become a major issue in the management of hypertensive patients. Numerous studies have demonstrated that the major problem is the lack of persistence followed by a poor day to day execution of the prescribed regimens. Although there are multiple ways of assessing drug adherence, only very few of them are accurate and the most accurate ones are either difficult to implement in clinical practice or too expensive and hence not available outside reference centers. Therefore, physicians have no real capacity to establish a correct diagnosis of non persistence or poor adherence even in high risk patients such as those with resistant hypertension. Today a new approach is becoming increasingly used which consists in measuring urinary drug levels. Nevertheless, there is still an important need for simple and cheap techniques or devices helping physicians in their ability to tackle poor adherence to therapy and thereby improve blood pressure control in the population.