Highway figures for fatal injury-producing traffic crashes and for resulting deaths and injuries were compiled from records of the Arizona Department of Transportation for the period covering January 1982 to December 1988. Interrupted time-series methods were used to measure changes in pre-post law periods. Traffic crashes increased by 32 percent after the new law, while deaths and injuries rose by 36 percent. At the same time, no appreciable increase in traffic crashes or casualties was measured for Arizona's urban interstate highways on which the maximum speed limit remained at 55 mph. The analysis further showed that the increase in traffic casualties following the new law was permanent. Through December 1988, over 1,000 deaths were attributed to the higher speed limit. An additional 3 deaths and 50 injuries occurred on Arizona's rural interstates in each month since the 65 mph speed limit became law. The report concludes that these casualties would not have occurred if the speed limit remained at 55 mph. 1 reference, 1 table, 4 figures.