The state-of-the-art understanding of rollover of the commercial vehicle is reviewed. Accident statistics are presented which highlight the severity and lethal nature of rollover crashes. Physical and statistical evidence for the linkage between vehicle roll stability and the actual occurrence of rollover accidents is presented. The fundamentals of static roll stability are described in detail and then enhanced with discussion of dynamic considerations of the rollover process. The text concludes with a discussion of the evolving use of intelligent electronic systems and active vehicle control for reducing the occurrence of rollover. Appendices include a bibliography of the literature on heavy-vehicle rollover.