Objective To evaluate the value and limitation of primary MSCT examination for rib fractures in a short interval. Methods Seventy-two cases with rib fractures were analyzed retrospectively.All of them underwent primary MSCT examination within the three days after trauma,and MSCT examination of chest,epigastria,rib or X-ray examination of rib for 1-6 times in the following 8 weeks.41 cases underwent X-ray examination firstly before MSCT examination.The total number of rib fractures was determined according to the compositive results of every examination.Diagnosis rate of the primary MSCT and X-ray examination were compared with each other.Results Among 72 cases,404 fractures in 325 ribs were diagnosed.Primary MSCT diagnosed 305 confirmed fractures and 28 doubtful fractures,and 84 fractures were not detected with diagnosis rate of 75.5%.13 of 28 suspected fractures were ruled out by the following re-examinations.The MSCT and X-ray diagnostic rates were 72.1%、50.3%,respectively for 41 cases who underwent X-ray examination firstly.Four fractures showed by X-ray plain film were not shown by primary MSCT.Conclusion There is a certain proportion of cases diagnosed as obscure or doubtful rib fracture by the primary MSCT. Therefore,diagnosis should be closely combined with the re-examination results of MSCT and X-ray plain film,especially MSCT ex-amination between the fourth and eighth weeks after trauma.