OBJECTIVE: 1. To determine the difference of scapulohumeral rhythm (SHR) between the affected and unaffected side in hemiplegic patients. 2. To discover the influencing factors on altered scapulohumeral rhythm of affected side in hemiplegic patients. METHOD: Fifteen hemiplegic subjects, 18 to 54 years of age, participated in this study. Subjects were divided into two groups according to muscle tone on the basis of modified Ashworth scale (MAS). Plain X-ray of the shoulders were taken in neutral, 90 degree abduction, and full elevation of the arm in both affected and unaffected side. The arm angle, scapula angle, and glenohumeral angle were recorded for each individual in each of the three positions. RESULT: In the unaffected shoulders of hemiplegic patients, the mean values of SHRs from neutral to the 90o and from neutral to the 180o were 1 : 1.82 and 1 : 2.12, respectively. In the affected shoulders, the mean values of SHRs between 0~90o abduction and 0 to full abduction were 1 : 2.35 and 1 : 2.25, respectively. The mean value of SHRs from neutral to 90 degree of affected side was significantly decreased than unaffected side in the low tone group and increased in the high tone group (p<0.05). In addition, the SHRs of hemiplegic shoulders were significantly increased in the high tone group than the low tone group (p<0.05). CONCLUSION: Spasticity tends to result in decreased motion of scapula, which alters the SHR. A glenohumeral-to-scapulothoracic ratio of hemiplegic shoulder could be affected by spasticity and presence of subluxation.