The pelvis is a ring structure with strong ligamentous support. This support includes the symphysis pubis, the anterior and posterior sacroiliac ligaments, and the strong sacrospinous and sacrotuberous ligaments. Since the pelvis is a ring, disruption of any portion of the ring is always associated with disruption in another portion of the ring. Massive pelvic disruption is an important and often life threathening. The author reviewed 36 cases of unstable pelvic bone fractures treated at the Orthopedic department of Chonbuk National University Hospital from January 1982 to December 1989, and analized the causes of injury, types of fracture by Pennal and Tiles method, associated injuries, early and late complication, methods of treatment. The clinical results were obtained as follows: 1. The incidence of injury in male was almost same in female and most of the patients were in the 3rd to 5th decade of their life. 2. The causes of injuries were traffic accidents, fall-down, others. 3. The most common fractures of unstable pelvic bone fractures were type II fractures due to lateral compression and Type III fractures due to vertical shear(Br Penall and Tile). 4. The fractures of acetabulum and tibia and fibula were the most commonly associated bone and joint injuries. Also the injury on the genitourinary tract was the most commonly associated soft tissue injuries. 5. There are various mathods of treatment in unstable pelvic bone fracture. A satisfactory results of conservative treatment were 73% and operative treatment were 85%. 6. In unstable pelvic bone fractures we consider that the external fixstior should probably be the first choice of treatment.