Congenital muscular dystrophy is one of the most frequent and severe childhood muscular dystrophies. Several forms of this disease have been described. The form associated with marked central nervous system disturbances, frequent in Japan, is known as Fukuyama congenital muscular dystrophy and was recently linked to chromosome 9. The most frequent form observed in occidental countries appears to be clinically characterized by exclusive involvement of skeletal muscle, and has been identified by clinico-pathological features which are often fallacious. A predominant histopathological feature is the marked increase in endomysial collagen tissue. We investigate whether laminin, a major component of the extracellular matrix, which is linked to the subsarcolemmal cytoskeleton by a large oligomeric complex of dystrophin-associated glycoproteins, could be involved in this form. We observed a specific absence of merosin, the laminin M chain, in 13 patients affected by classical non-Japanese form of congenital muscular dystrophy. This result allows the precise identification of a particular form of congenital muscular dystrophy and gives a clue to understanding its molecular pathogenesis.