Essential Hypertension is a major health problem due to its serious complications on various body systems especially cardiovascular system. An (I/D) polymorphism of ACE gene was found to be associated with pathophysiology, complications of hypertension so this study was done to explore this association and may help in treatment of hypertension. The book contains a background of the disease (introduction), methodology of how the study was done, results and our future recommendations. Doctors in many fields will benefit from this book espicially cardiovascular ones in treatment of disease.