Objective To evaluate the clinical importance of doublecontrast CTdiagnosis of traumatic anterior shoulder instability. Methods Forty-eight patients underwent double contrast CT scan. With the guide of CT scan, anterior arthrocentesis of the shoulder was performed and 4 ml of 76% urografin was injected into the joint and then 10 ml of filtrated air was injected. The patients wereexamined by SOMATOM CR Systematic CT. The results of double contrast CT of the 48 patients were divided into Ⅰ, Ⅱ and Ⅲ degree according to the CT results related to their injury history, clinical symptoms, signs and operation findings. Results The patients had no complaint after the CT examination exceptfor 3 patients, who had slight pain within 2 days after CT examination. The results of double contrast CT were as follow:Ⅰ degree: 9 patients, Ⅱ degree: 22 patients, and Ⅲ degree: 17 patients. All patients with Ⅰ degree injuries were treated with rehabilitation program. The patients with Ⅱ degree injuries were mainly treated withrehabilitation program, but took much longer time. The patients with Ⅲ degreeinjuries were suggested to be treated with surgery. Conclusion To divide the results of double contrast CT into Ⅰ，Ⅱ and Ⅲ degree not only reflects the severity of traumatic anterior shoulder instability but provides information for the treatment of the instability.