Morbidity and mortality from cardiovascular diseases are still high, despite the use of the best available therapies. There is growing evidence that excessive rennin-angiotensin system activation underlies much of the damaging and progressive nature of cardiovascular and kidney diseases. Today, ACE inhibitors and Ang II receptor antagonists have clearly demonstrated their efficacy in preventing target organ damage and in reducing cardiovascular morbidity and mortality in ischemic heart disease. The content of this book written to explore the anti ischemic properties of ACE inhibitors and ARBs with respect to free radical scavenging properties. This type of mechanism based research works will improve the basic idea to develop the cardiovascular research. More importantly, the results of such will provide us with better cost effective and socially acceptable therapeutic options for a disease, which threatens to be the number one killer disease in this century.