The book begins with a general overview of Warburg Hypothesis, mitochondrial structure and function, and then outline more specifically the metabolic and molecular alterations in mitochondria that are associated with human cancer and their clinical implications. An emphasis is also placed on mtDNA mutations and their potential role in carcinogenesis. The potential use of mitochondria as biomarkers for early detection of cancer, or as unique cellular targets for novel and selective anti-cancer agents will also be discussed.