Electron-microscopic X-ray microanalysis has been used to compare elemental concentrations in specific organelles in normal and diseased human muscle. An elevated calcium to phosphorus ratio has been found in both myonuclei and interstitial cell nuclei in diseased muscle compared with controls. Preliminary observations also suggest that differences in elemental concentrations may be associated with structural abnormalities such as internal nuclei, and loss of myofibrils.