The term "myofibrillar myopathies (MFM)" was proposed in 1996 to a group of myopathies that have common pathological changes. The muscle biopsy shows cytoplasmic hyaline inclusions with various sizes and shapes, best observed in trichrome-stained sections. Immunohistochemical study shows deposits of desmin and some sets of myofibrillar and non-myofibirllar proteins in or around these inclusions. The electron microscopy displays unique dappled and electron-dense structures. MFM mutations have been identified in genes encoding desmin, αB-crystallin, myotilin, ZASP, filamin C, Bag3 and FHL1. They are proteins present in the Z-disk, which correlates the findings suggesting that disruption the Z-disk occurs first, followed by accumulation of degenerative products of myofibrils. Some of the gene products are essential for maintaining the structural integrity of myofibrils against mechanical stress, and others function as a molecular chaperone or a co-chaperone. In the latter cases, apoptotic or pre-apoptotic myonuclear changes are frequently found. The gene abnormalities await to be determined in more than a half of MFM patients. Although clinical features are variable in MFM as a whole, they show some homogeneity in mutations of the same molecule. We must note that MFM patients are often associated with cardiac conduction defects, cardiomyopathy and respiratory insufficiency.