Muscles from two cases of osteomalacia were studied histochemically and electron-microscopically. Histopathological finding were common in these two cases. There are (1) myopathic changes such as scattered muscle fiber atrophy, necrosis, and internal uuclei, (2) derangement of intermyofibrillar network. and (3) type II fiber atrophy. Electron-microscopical finding corresponded well with light microscopical findings. These are distinct pathological features and deserves to be called osteomalacic myopathy. As the pathogenetic mechanism of this myopathy, phosphate depletion in the muscle cells resulting in disturbed glycolysis, and decreased vitamin D effects on muscle cells resulting in diminished calcium uptake by sarcoplasmic reticulum, are considered to be the most important two factors.