The author analyzed detailed pattern of pelvic bone fracture in 52 cases of posterior urethral injury associated with pelvic bone fracture in male. The relationship between fracture and urethral injury was reviewed in 38 cases who received retrograde urethrography at the time of injury. the pattern of urethral injury due to pelvic bone fracture was newly classified. The results were as follows : 1. In age distribution, the most common was 5th decade (26.9%). 2. The most frequent type of pelvic rami fracture was two rami fracture (52%). 3. There was no case with only the superior rams fracture, and all cases were associated with inferior ramus fracture with or without superior ramus fracture. 4. In inferior ramus fracture, the ratio ischial ramus fracture to pubic ramus fracture was 46.1 : 17.4. 5. In cases with only the ischial ramus or pubic ramus fracture, unilateral fracture exceeded bilateral fracture (44.2 : 19.3). 6. The bladder rupture was found in 10 among the total 52 cases, 9 of which were associated with superior ramus fracture, and 8 were extraperitoneal type. 7. The most common type of urethral injury was Type III (73.7%), and followed by Type II (10.5%), Type I (7.9%), and Type IV (7.9%). 8. These results strongly suggested that the superior ramus fracture was related to bladder, rupture, and inferior ramus fracture to urethral injury.