Hypertension, also referred to as high blood pressure, is a disease afflicting almost 1 billion people world-wide. Some 70 million adults in the United States are affected by hypertension. The condition also affects about two million teens and children. It is called the "silent killer" due to the deleterious damaging effects, such as stroke, myocardial infarction, renal dysfunction, visual problems, among others, derived from hypertension. It is noteworthy that one-third of patients in this condition are not even aware they are hypertensive, as this disease is usually asymptomatic for many years, even decades, until it finally damages certain critical organs and the only reliable way to detect its occurrence is to regularly check blood pressure. Therefore, considerable effort has been devoted to ascertain the causes of hypertension, as well as the mechanisms damaging the organ function. Nevertheless, about 95% of cases have unknown causes and represent the primary or essential hypertension. This book presents an update of research advances contributing to a better understanding of relevant clinical models of hypertension, particularly; the involvement of the role of oxidative stress in various forms of hypertension as a still emerging subject. This paradigm could be applied to account for blood pressure elevation in the metabolic syndrome, renovascular disease, preeclampsia and chronic kidney disease, among others. These examples are discussed in the light of recent clinical and experimental studies providing a rational base for diagnosis and treatment of the diseases. Each chapter includes a synthesis of the mechanistic approach supported by the accumulated evidence to facilitate its comprehension.