The electromyogram is gaining importance as a diagnostic tool in the clinical practice of orthopedic surgery. Its uses in the area of kinesiology will undoubtedly be further developed in the future in ways which can be standardized and made available to the practicing orthopedist to improve the results of muscle and tendon surgery and the design of surgical procedures. It should be noted that in either case electromyograms can be utilized to give a great deal of valuable information concerning the competence of the motor unit, the functioning mass of muscle fibers and the phasic relationships of muscle groups. Its value in diagnosis, however, depends directly upon the care with which it is performed, the patience of the electromyographer in sampling an adequate quantity of muscle mass to be certain that nothing has been overlooked and, above all, the specificity of the orthopedic surgeon in delineating exactly what information he wishes to obtain, so that the performance of the electromyogram can be confirmed and aimed directly at producing answers to the questions he is asking. In this regard, the electromyogram is in no sense a screening test or a catchall which the orthopedic surgeon can substitute for a careful clinical evaluation.