Muscular cell integrity is assured by a number of proteins of different structure, function and localization. Their defective synthesis of genetic background results in muscular dystrophies. In these diseases progressive damage of skeletal muscle leads to disability, and in some cases affection of respiratory muscles may be a cause of early death. There is no doubt now that proper muscle function demands undisturbed collaboration of a great number of proteins, located inside the cell as well as in sarcolemma and extracellular matrix. This collaboration ensures appropriate indispensable communication of the muscle cells with their external environment. Molecular background is well known for the most common Duchenne muscular dystrophy and Bethlem myopathy, both resulting from a damage of dystrophin. Less is known about sarcolemmal and extracellular matrix proteins. Defects in collagen VI and laminin, proteins responsible for a proper anchoring of the cell in extracellular matrix, result in Ullrich muscular dystrophy, Bethlem myopathy and merosin-dependent muscular dystrophy MDC1A. Among proteins localized in sarcolemma, defects resulting in muscular dystrophies were found in integrins and a complex of sarcoglycans, four proteins responsible for stabilization of dystrophin-glycoprotein complex in the cell membrane. A special group of muscular dystrophies called dystroglycanopathies is a result of defective glycosylation of a-dystroglycan. Uncovering the molecular background of muscular dystrophies brings a hope for novel therapies, creating molecular by-passes omitting defective proteins and limiting disease progress and patients disability.