Symphyseal injury is increasing in number together with today's speed of development of car industry in Korea. However, this injury is not common in practice. Some authors reported that symphyseal injury is only 4 to 6% of all pelvic fractures. Symphysis pubis has characteristicsl anatomy to maintain mechanical integrity of the pe1vis with circumferential ligament. The pelvis is a ring structure with strong ligaments. This support include the symphysis pubis, the anterior and posterior sacroiliac ligaments, and the strong sacrotuberous ligaments. According to Peltier(1964), when symphysis is separated more than 1.0cm, pubic instability will be developed. However, Wild(1982) reported that pelvic instability develops when separation of the symphysis exceeds more than 2.5cm. Tile(1984) reported that anterior pubic rami acts as a strut to prevent anterior collapse of the pelvic ring during weight bearing. However, in the presence of intact posterior structures, it gives little effect on pelvic stability. In addition to trauma, pelvic instability develops congenitally or by pregnancy. During pregnancy, pregnancy-related hormones relsx the ligameritous stuctures of the pelvic girdle. In most instances, the major pelvic ring returns to normal when the effect of the relaxin hormones disappear. However, in rare instances, a major symphysis disruption may continuously persist. To evaluste the trauma-induced separation of the symphysis pubis, we analyzed the 19 cases with 15 months follow-up on an average, who were treated at the Orthopaedic Department, Kang-Nam St. Marys Hospital, from June 1981 to June 1986. The results were as follows 1. Among 19 cases, 9 cases(47.4%) were male, 10 cases(52.6%) were female. And average age of the patients was 30.2 years. 2. The main cause of the fracture was traffic accident in 18 out of 19 cases. 3. In cases of symphyseal separation more than 3.4cm, fracture-separation of both sacroiliac joint was certainly occured. However, in cases with separation more than 2.2cm, unilalateral fracture-dislocation of sacroiliac joint occurred. 4. Open reduction and interal fixatiopn including external fixation was performed in 9 og cases. As an indication of surgery, separation of the symphysis, which exceeds more than 2.2cm and which associated (1) with sacroiliac fracture-dislocation, (2) failed conservative treatment, and (3) when simultaneously emergency urological operation is indicated.