This addition to the classification of myopathies is a result of the improved diagnostic techniques in muscle pathology in recent years, largely through the application of electronmicroscopy and histochemistry. After summarizing the clinical picture, the authors call for classification: (1) Congenital myopathies due to developmental arrest: myotubular myopathy, congenital fiber type disproportion. (2) Congenital myopathies due to persistent organellar regression: focal loss of cross striation, myopathy with lysis of myofibrils, nemaline body myopathy, zebra body myopathy, spheroid body myopathy, myopathy with tubular aggregates, satellite cell myopathy. (3) Congenital myopathies due to metabolic errors: mitochondrial myopathy, mitochondria-lipid-glycogen disease. (4) Congenital myopathies due to the lack of the trophic influence of innervation: central core disease, multicore, minicore disease. These congenital myopathies have been taken from the ill-defined heterogeneous conglomeration known as amyotonia congenita or floppy infant syndrome and given a place of their own.