A review of US mortality data from 1979 to 1986 identified 15,194 deaths and nearly 600,000 years of potential life lost before age 65 years that were associated with head injuries from motorcycle crashes. White males from 15 to 34 years of age accounted for 69% of the deaths. The rate of motorcycle-related deaths associated with head injury declined modestly between 1979 and 1986 (19% using rates based on resident population and 8% based on motorcycle registrations). Population-based rates adjusted for age, sex, and race in states with partial or no motorcycle helmet-use laws were almost twice those in states with comprehensive helmet-use laws. Two states that weakened their helmet-use laws from comprehensive to partial during the study period had increases in motorcycle-related head injury death rates (184% and 73%), and one state that strengthened its law from partial to comprehensive had a decline in its death rate (44%). Head injury death rates based on motorcycle registrations were also lowest in states with comprehensive helmet-use laws. Since helmets reduce the severity of nonfatal head injuries in addition to lowering the rate of fatal injuries, we urge the adoption and enforcement of comprehensive motorcycle helmet-use legislation.