Fractures of the pelvis are usually devided into two types, so called stable and unstable, according to the degree of instability of the pelvic ring, the major forces acting upon a hemi-pelvis and existence of the open wound. The unstable fracture has the breakage of ring stucture, which may by associated with injury of internal organ and massive pelvic bleeding. The authors reviewed 17 cases of the unstable pelvic fracture treated by Hoffmann's or Slatis external fixateurs at the orthopedic department of Eul Ji General Hospital from January 1988 to February 1991. Types of fracture were two straddles, six vertical shearings, three pelvic dislocations, three lateral compressions, four bucket-handles, one total disruption. Operation timing was between 2 and 13 days(mean 5 days) after injury. The devices were removed between 10 and 16 weeks (mean 12.7 weeks) postoperatively. Mean follow-up period was 1 year and 7 months-from 1 year to 2.2 years and analized with the residual pain, limping and staus of anatomical reduction. The results showed that eleven patients were excellent, seven good, two fair and one poor which was associated shortening of femur by comminuted fracture. The patient could ambulated with partial supporting at mean 6 weeks postoperatively. There was not any postoperative infection.