PURPOSE: Rollover motor vehicle crashes have a higher injury severity and fatality than other motor vehicle crash types. From a left-quarter turn rollover accident of 25-passenger bus, we intend to assess the injury of the occupant and the injury severities according to the occupants' position. METHODS: We carried out the 3 steps investigation of occupants' interview, visiting the repair shop and using the police report. We analyzed injuries sustained by occupants, and compared injury severities considering column, row in occupant's position and passenger interaction. RESULTS: The rollover involved 14 passengers in the bus who were all old women except a man driver. The most common injury was in the upper extremity, with six occurrences being a left clavicle fracture. Major injuries including hemothorax and pneumothorax were diagnosed at left side of the occupant. In the comparison of injury severity among driver's column (left side), mid column and passengercolumn, ISS of passenger column was the highest (9.9+/-7.4, 8.8+/-5.5, and 10.3+/-4.0, respectively, p>0.05). The injury severity of multiple occupants by row was higher than that of single occupant (10.8 vs. 3, p<0.05). CONCLUSION: An occupant must fasten their seat belt to prevent an injury by passenger interaction in the left-quarter turn rollover accident of a bus.