The authors compared US motor vehicle and motorcycle mortality rates during periods when each of several alcohol-related laws were in effect with mortality rates during other periods. During the period 1980-1997, there were 792,184 deaths due to motor vehicle crashes and 63,052 deaths due to motorcycle crashes. An estimated 26% and 49% of these fatalities, respectively, were attributable to alcohol use. The incidence of alcohol-related mortality in motor vehicle crashes was lower when laws specifying a blood alcohol concentration of 0.08 g/dl per se (laws stating that it is a criminal offense to drive with a blood alcohol concentration above the state's legal limit) were in effect (adjusted rate ratio (RR) = 0.86, 95% confidence interval (CI): 0.83, 0.88). For motorcycle deaths, the adjusted rate ratio was 0.87 (95% CI: 0.79, 0.95). The incidence of alcohol-related mortality in motor vehicle crashes was also lower during periods when two other types of laws were in effect: zero tolerance laws (adjusted RR = 0.88, 95% CI: 0.86, 0.90) and administrative license revocation laws (adjusted RR = 0.95, 95% CI: 0.93, 0.98). Overall motorcycle mortality was lower when administrative license revocation laws were in effect (adjusted RR = 0.95, 95% CI: 0.92, 0.98).