Selected automated accident data files, including DOT's FARS and the state files of Texas and Michigan were examined to determine what percentage of heavy truck accidents-involve significant injury to truck occupants, and which subsets of these are amenable to application of occupant crash protection technology. Rollovers, because of the relatively high likelihood of severe vehicle damage and serious injuries, and frontal impacts because of their high incidence, were chosen as targets for further study. Details of injury causation were provided by analyses of the CPIR-B heavy truck file, which was recoded for the study. Consistent with previous studies of heavy truck injury causation, the primary injury sources were identified as ejection, entrapment, and contact with the steering assembly. Relative to injured drivers of other vehicle types, heavy truck occupants were found to be more prone to multiple injuries, resulting in part from the multiple-impact nature of heavy truck accidents. Arguments are presented for the development of useable restraint ststems and collection of more detailed accident data as the next steps in the area of heavy truck occupant crash protection.