Pelvic fractures in general can be divided into two major types, based on the amount of energy involved : low-energy mechanisms are usually fractures of individual bones of the pelvic ring and high-energy mechanisms results in more severe injury to the pelvic ring, generally producing pelvic ring disruption. Pelvic fractures resulting from low-energy mechanism are usually fractures of individual bones of the pelvic ring that do not damage the true integrity of the ring structure. These include avulsion fractures, isolated fractures of the sacrum, and iliac wing fracture. Computerized tomography permits confirmation of findings noted on plain film and delineates injury to the posterior ring. It facilitates subclassifying the fracture according to degree of severity, as in the Young classification. The purpose of this study is to evaluate the role of CT, which is to identify the combined injuries of pubic ramus fractures. The sacrum impacted fracture and sacroiliac joint injury are often unidentified and diagnosed as an isolated fracture to the pubic ramus. The 42 cases of pubic ramus fractures on conventional radiography were simultaneously performed CT from June 1996 to February 1998. The results of associated injuries were as follows. 1. In 34 cases (81%) posterior pelvic ring injuries (sacral fractures 28 cases, anterior sacroiliac joint widening 6 cases) were observed. 2. CT was very useful to diagnose the posterior pelvic injury and to determine the mechanisms of injury.