OBJECTIVE To review the up-dated classification of limb girdle muscular dystrophies (LGMDs) in relation to the defective protein and the genetic abnormality. To explain how these proteins are related to dystrophin and to the proteins of the extracellular matrix. To show that an accurate diagnosis is necessary and that it can be adequately made in neuromuscular pathology laboratories. METHODS We present a study of the different types of LGMDs, dystrophinopathies and congenital muscular dystrophy. We emphasize the recent events which concluded in the identification of these disorders, the genetic alteration, the defective proteins and, briefly, the clinical features. CONCLUSIONS The recent identification of numerous skeletal muscle proteins and of the codifying genes made possible a new classification of a large group of muscular dystrophies. The possibility to study these proteins on the muscle biopsy with immunohistochemistry and Western blot techniques indicates the need of an accurate diagnosis in specialized neuromuscular laboratories. Since there is a great number of genes discovered and of mutations within the same gene, and the clinical picture of different diseases can be similar, a previous study of the protein is advisable as a guide for a further genetic study.