Since 1975, 26 states have repealed or modified their motorcycle (M/C) helmet laws. Louisiana (LA) reinstated the M/C helmet law in 1982. The medical and financial impact of repeal in Kansas (KS), reinstatement in LA (accident, fatality, and critical injury rates) have been studied through 1987. Current FARS data and studies from KS, LA, 10 states and 5 countries are compared and reported. Without M/C helmet legislation, the user rate drops from 99% to 50%. With reinstatement, the user rate rises to greater than 95%. Average hospital stay (days) for helmeted (H) riders is 5.8, non-helmeted (NH), 11.8. Fatality rate/1,000 M/C registrations is 6.2 NH, 1.6 H. Changes effected through M/C helmet legislation: fatality rate was 1.17 (1981), falling to 0.44 (1987) with legislation (62% decrease) (LA); 66% change Colorado, 42% Oklahoma; fatality rate/1,000 accidents changed 28% from 42.68 NH to 30.81 H; injury accidents 84% to 73%, critical injury reduction 44% (1981 to 1987). Risk of head injury: NH 2.07 greater than H. Risk of a fatal accident: NH 1.44 greater than H. Accident rate is less with M/C helmet legislation than without (19% KS, 48% LA). The medical costs (LA 1981 to 1987) decreased 48.8%. Length of stay decreased 37%. The major impact hospital stay greater than 20 days: 80% decline. Cost of long-term disability greater than 30 days: 81.2% decrease (LA). Average disability was 26.7 vs. 51.1 days (KS); 25.5 H required hospitalization per 100 accidents vs. 41.6 NH. Medical costs: NH 306% greater than H (KS). Based on 1989 dollars, $120.8 million of additional medical care and rehabilitation expenses/per year were due directly to non-use of helmets (U.S.); 60-82% of NH riders have no insurance; $4.9 billion was absorbed by the public in the form of increased taxation, higher insurance costs, and lost taxes. M/C helmet legislation decreases medical costs. In this era of spiraling health care costs, legislation mandating the use of protective helmets should be considered as a viable alternative to raising taxes.