Outstanding improvement has been made in the molecular understanding of several muscle diseases with the application of molecular biological techniques to the investigation of human disorders. The identification of genetic mutations has improved considerably the diagnostic approach to muscular dystrophies, mitochondrial myopathies and ion channel disorders. Important results have been achieved in the field of inflammatory myopathies. With a few exceptions, therapies available are nonspecific and rarely represent a cure for the disease. Molecular medicine offers an opportunity to design new therapeutic strategies based on the pathogenic mechanisms underlying each disease.