Bioenergetics has developed into a new molecular era of structure and function analysis of the membrane protein complexes involved in energy transduction. In parallel, this allows a deeper understanding of the human mitochondrial myopathies. Extensive studies have mapped numerous point mutations and rearrangements in the human mitochondrial DNA (mtDNA). However, the mechanism of expression of the pathologies is not well understood in most of the cases. In addition, a new challenge is the mapping of human nuclear mutations affecting the mtDNA and the mitochondrial metabolism. With the accomplishment of the Human Genome Project, the new genomic era will contribute significantly to these studies. This book reviews recent advances in these subjects. The actual status of the research in this important subject is analyzed in order to evaluate the knowledge in the molecular mechanisms of these pathologies, the possibility of predicting the severity of mutations carried by newborns, and the possible options for effective treatment for these patients, including the scope of future advances in gene therapy. This book will be one of interest to a growing number of researchers and students studying mitochondrial myopathies, including groups of bioenergetics, molecular biologists, biomedical researchers, and physicians working in this field. Contents: Stability and deleterious rearrangements of human mitochondrial DNA; Nuclear genes affected in human mitochondrial deficiencies: perspectives from the human genome sequence; Complex I. Structure, function and deficiency; Complex II. Structure, function and deficiency; Complex IV. Structure, function and deficiency; Mitochondrial ATP synthase: structure, function and assembly in human cells; Human ATP6 mutations: molecular mechanism of pathology according to a topography model of human subunit 6; Transfer of mitochondrial genes to the nucleus: perspectives for alltopic expression of mitochondrial proteins and for mitochondrial gene therapy.