Background: Conventionally, there are many studies about efficacy of muscular assessment for throwing shoulder injury. On the other hand, there are few reports regarding utility of the self-assessment for throwing performance. In this study, we report whether the evaluations of muscular strength of the shoulder joint contribute to the throwing performance.<BR>Methods: 132 pitchers affiliated with a certain prefecture high school baseball federation in 2011 had a medical checkup performed, evaluated items were examined and shoulder strengths measured. Prone internal rotation (IR), prone external rotation (PER), seated external rotation (SER), and supraspinatus (SS) strength were tested. Each player was also surveyed on their pitching performance by a questionnaire at the examination. All players were male, the average length of their baseball career was 8.3 (1 ∼ 12) years. The pitchers were divided into two groups; good performance group, group G, and wrong performance group, group W. Moreover, the pitchers also divided into two groups; the pitchers who had shoulder pain at the time of pitching, group S, and the pitchers who had no shoulder pain, group N. Student-t test and Mann-Whitney U test were used to compare the differences between these two groups.<BR>Results: 25 pitchers (18.7%) had shoulder pain at the time of pitching. The significantly item about classification of the performance of the pitcher was the abduction strength ratio.<BR>Conclusion: The evaluation of abduction strength may be important when a baseball pitcher cares for the environment of the shoulder joint.