The purpose of this study was to determine the isokinetic strength of the shoulders of high school and college-aged baseball pitchers. Twenty-four athletes ranging from 14 to 21 years of age volunteered for this study. The Cybex(R) II and U.B.X. T. were utilized to test the strength of the shoulder abductors/adductors, flexors/extensors, horizontal abductors/adductors, and external/internal rotators at 90, 120, 2 10, and 300 degrees /sec. There were no consistent differences between dominant and nondominant arm strength, except for the shoulder adductors and shoulder extensors. The shoulder abductors and flexors were approximately 50% as strong as the adductors and extensors, respectively. There was a 1:1 ratio between the horizontal abductors/ adductors. The external rotators were approximately two-thirds as strong as the internal rotators. A positive correlation was found between total body weight and shoulder strength. This information is relatively new to the literature and should provide clinicians with some training and rehabilitation guidelines. J Orthop Sports Phys Ther 1986;7(4):163-172.