Weakness of abduction strength was often seen in shoulder patients. The causes were various, such as rotator cuff insufficiency, pain, instability, limited ROM, paralysis and disuse. We hypothesized that abduction strength might reflect a shoulder condition. The purpose of this study was to clarify whether abduction strength could become an indicator to express a shoulder function. We studied 57 patients (38 males and 19 females) with shoulder disorders. The average age was 36 years old. 25 shoulders had anterior instability, 21 shoulders had rotator cuff tear, 5 shoulders had throwing injury and 6 had other problems. Preoperative isometric abduction strength was measured at 90 degree abduction with a hand-held dynamometer (MicroFET). We calculated the ratio between the strength of the affected shoulder and the non-affected shoulder. As the methods for evaluating the shoulder function, we used the Japanese Orthopaedic Association scoring system for shoulder disorders (JOA score), The American Shoulder and Elbow Surgeons shoulder evaluation form (ASES), Constant score and Simple Shoulder Test (SST). We analyzed correlations between abduction strength and the score of each evaluation method using Pearson's correlation coefficient. The average ratio of abduction strength was 0.711(0-1.16). According to the average scores of evaluation methods, JOA score was 72.1, ASES 58.9, Constant score 70.8 and SST 7.6. The correlation coefficients between abduction strength and the scores were as follows: JOA score 0.716, ASES score 0.712, Constant score 0.810 and SST 0.744. There were significant correlations between abduction strength and the scores (P<.0001). The results of this study have shown that there were strong significant correlations between abduction strength and the scores of evaluation methods. It suggested abduction strength could become an indicator to express a shoulder function.