BACKGROUND: Previous studies have examined the independent effects of occupant height, obesity, and body mass index in motor vehicle collisions and identified related injury patterns. The hypothesis of this study was that as the driver's body habitus diverges from the 50% percentile male Hybrid III Crash Dummy (H3CD), the frequency of injury changes. METHODS: The 1995 to 1999 National Automotive Sampling System Crashworthiness Data System was used. Study entry was limited to restrained drivers who were then subdivided into height and weight categories. Incidence rates were calculated for injuries to selected body regions as defined by the Abbreviated Injury Scale for overall, frontal, and driver's side collisions. RESULTS: When grouped according to height and weight as descriptors of body habitus, injury rates for restrained drivers were increased as well as decreased in several subgroups. This association was seen in overall, frontal, and driver's side collisions. CONCLUSION: The H3CD plays a major role in vehicular cabin interior design and crash testing. For drivers with a body habitus different from that of the H3CD, the vehicle cabin/body fit changes and the safety features may perform differently, which could account for these observations.