Per vehicle crash involvement rates were compared for otherwise identical vehicle models with and without electronic stability control (ESC) systems. ESC was found to affect single-vehicle crashes to a greater extent than multiple-vehicle crashes, and crashes with fatal injuries to a greater extent than less severe crashes. Based on all police-reported crashes in 7 states over 2 years, ESC reduced single-vehicle crash involvement risk by approximately 41 percent (95 percent confidence limits 33–48) and single-vehicle injury crash involvement risk by 41 percent (27–52). This translates to an estimated 7 percent reduction in overall crash involvement risk (3–10) and a 9 percent reduction in overall injury crash involvement risk (3–14). Based on all fatal crashes in the United States over 3 years, ESC was found to have reduced single-vehicle fatal crash involvement risk by 56 percent (39–68). This translates to an estimated 34 percent reduction in overall fatal crash involvement risk (21–45).