ObjectiveTo assess the credibility of the ABC Classification for acetatbular fractures. MethodsThe data of 60 patients were randomly chosen from a total of 1 122 patients with acetabular fractures, who were classified according to ABC Classification, with each subtype including 20 cases. The 60 cases were divided into two groups: X-ray (Pelvis AP, oblique position of iliac bone and oblique position of obturator foramen radiographs without CT) and X-ray+CT (plain radiographs with 2D-CT). Nine surgeons, including 3 with 1-5 years’ experience, 3 with 5-10 years’ experience and 3 with 10-15 years’ experience, were asked to make diagnosis for the two groups using ABC Classification system. Each surgeon read the radiographs twice at a 3-month interval without knowledge of other clinical data. The order of the radiographs was changed in the second review. The results of the two sessions were analyzed and the inter- and intra-observer reliability and reproducibility were evaluated using Kappa test. ResultsThe inter-observer reliability during the two sessions were 0.66 (0.71) in X-ray group and 0.67 (0.72) in X-ray+CT group. Intra-observer reproducibility during the two sessions were 0.75 in group X-ray and 0.78 in X-ray+CT group. The diagnoses of surgeons with longer experience had higher credibility and reproducibility. ConclusionABC Classification can obtain high reliability diagnosis for acetabular fractures. CT is valuable for treatment of acetabular fracture, but it can not greatly increase the credibility of ABC Classification.