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We investigated motorcycle rider death rates between states with full motorcycle helmet laws and those without. This was done using both unadjusted bivariate analyses and multivariate random-effects generalized least squares regression models of rider death rates. Multivariate models were adjusted for the competing influences of several explanatory variables, including the existence of a motorcycle helmet law. From 1994 to 1996, states with helmet laws experienced a median death rate of 6.20 riders per 10 000 registered motorcycles and states without helmet laws experienced a median death rate of 5.07 riders per 10 000 registered motorcycles (P=0.008). After controlling for other factors that affect motorcycle rider fatalities (most notably population density and temperature), death rates in states with full helmet laws were shown to be lower on average than deaths rates in states without full helmet laws (P=0.740). Our study weakens the claim that rider death rates are significantly lower in states without full motorcycle helmet laws.