Of 149 large cities surveyed, 72 were found to have nighttime curfew ordinances applying to teenagers of various ages. The typical city curfew identified starts at midnight, ends at 5 A.M., and affects all activity of teenagers ages 13-17 in a public place and unaccompanied by a parent. In comparisons of 47 cities with curfews covering 13- to 17-year-olds and 77 cities without curfews, curfews were associated with a 23% reduction in fatal injury for 13- to 17-year-olds for the 9 P.M.-5:59 A.M. time period. This is identical to the 23% reduction estimated for both fatal and nonfatal motor vehicle injuries for 13- to 17-year-olds in an earlier, more limited study of curfews in Detroit, Cleveland, and Columbus, Ohio.