The application of dynamic integrated EMG and motion analysis to the shoulder has improved the understanding of dynamic shoulder biomechanics during athletic activities and rehabilitation protocols. These studies exemplify a symbiotic merger of basic science research and clinical application. EMG and motion analysis has produced specific objective quantifiable data concerning the muscles in and about the shoulder during normal planar motion, athletic motions, and rehabilitation exercises. This expanded understanding of intricate muscular interrelationships during athletic activities and rehabilitative exercises has not only complemented clinical awareness of subtle shoulder anomalies but helped to develop logical preventative exercises, surgical procedures, and rehabilitation protocols, all of which are based on sound scientific principles. Comprehension of the normal intermuscular interdependence during the previously mentioned activities has led us to investigate common athletic shoulder disorders. It is hoped that application of the normal EMG and motion analysis to the pathologic state will enable us to suggest new ideas concerning the pathomechanics of these disorders, as well as propose future treatment and rehabilitation of these maladies. The specific emphasis in this article has been the role of integrated EMG and motion analysis in the evaluation of athletic activities and rehabilitation exercises. It is hoped that knowledge of these investigations will increase the clinician's basic understanding of the biomechanics of the shoulder and aid in his or her clinical evaluation, treatment, and subsequent rehabilitation of the shoulder.