Given the large size and weight of heavy trucks, also known as tractor-trailer vehicles, a serious safety threat can be posed to the vehicle’s occupants in the event of a rollover collision. This study evaluated heavy vehicle accidents from 1994-2002 by submitting queries to the Fatality Analysis Reporting System (FARS), which is administered by the National Highway Traffic Safety Administration (NHTSA), in order to determine the number of incapacitating and fatal injuries that occurred when the occupants were contained in the cab during a rollover accident. The specific query was for rollover accidents of heavy trucks where the rollover was the most harmful event; the rollover was either the first or subsequent event; the truck received severe and disabling deformation; the occupants were not ejected; and the injuries sustained were either incapacitating or fatal. This rollover accident data was also compared with the total number of heavy truck accidents where incapacitating or fatal injuries occurred as reported by FARS for the 1994-2002 time period. The average percent of persons involved in accidents that matched the rollover query was 18%, with a high of 21% in 2002 and a low of 17% occurring in 1994, 1995, and 1997. The average percentage per year of incapacitating and fatal injuries for restrained occupants during this time period was determined by further analyzing the data obtained from the above stated rollover query and was found to be 35%. The conclusion drawn from this study is that significant injuries can occur from rollover accidents of heavy trucks even for restrained occupants. Rollover crashworthiness of heavy trucks is also evaluated in this paper.