Despite the high prevalence and heterogeneity of hypertension, blood pressure (BP) can be controlled to goal levels with effective therapy in many patients. However, in a small percentage of patients who have hypertension, the BP remains refractory to usual and customary therapeutic measures. In such patients, who have so-called “resistant” or “refractory” hypertension, proper evaluation and assessment have to be undertaken to improve the BP control. There are some factors that may make hypertension control difficult in some patients. Therefore, it is necessary to identify possible etiologic reasons for the loss of BP control and to rectify them to achieve normotension. In selected patients, aggressive treatment (nonpharmacologic and pharmacologic) of hypertension is required to prevent excessive morbidity and mortality.