Resistant hypertension (RHTN) consists in a condition where blood pressure (BP) levels remain uncontrolled despite the use of at least three drugs or if the control happens with four or more drugs. Throughout the last 50 years, it has been increasingly studied, and its phenotypes have been identified. The term refractory hypertension has been used concurrently with RHTN all those years, but in the last decade, it has been applied to the most afflicted part of RHTN--defined as the uncontrolled RHTN or as the uncontrolled RHTN who needs five or more drugs. Differences between those two phenotypes are being recently identified, especially classifying refractory subjects as having more: (1) cardiovascular risk, (2) target organ damage, (3) African-descending race, (4) coronary heart disease and myocardial ischemia, (5) aldosterone excess, (6) deregulation of adipokines, and (7) possible sympathetic hyperactivation. We review the most important studies in both resistant and refractory hypertension to gather the up-to-date data regarding the characteristics of these two high-risk groups of patients.