The fat embolism is a complication which occurs rarely in cases of long bone of lower extremity and pelvic bone fractures or after severe injury of soft tissue, and may result in an embolism in the lungs, brain, heart, kidneys and other important vessels when fat globules flow from bone marrow into such areas. There has been much adverse criticism about the pathogenesis of fat embolism including the incidence, diagnosis and treatment of it, and studies on this subject have been prevalent in recent years. The following results have been obtained through the study of 9 cases of fat embolism at the Department of Orthopaedic Surgery, Dong San Medical Center, Keimyung University during the period from 1973 to 1984. 1. By sex and age distribution, most of the patients were under the age of 40 and there were more male than female patients. 2. Seven cases were caused by traffic accidents and two were caused by falls accompanied by multiple fractures of the femur and pelvic bone. 3. Symptoms generally occured within 48 houres after trauma, however some cases were within 12 houres, some were 5 days and others 12 days. Clinical symptoms which were present at the time admission revealed increased erythrocyte sedimentation tates and decreased hemoglobin and platelete in most cases. Bilateral infiltrates and cotton ball appearances were found in all cases on thoracic radiology, but no fat globules were found in the urine or in frozen sections of clotted blood. 4. Blood gas analysis was performed in 4 cases and Pa02 under 60mmHg found in all cases increased gradually after treatment. 5. Of the 9 cases with fat embolism 6 cases completely recovered and three cases expired.