The purpose of this article is to determine and quantify the factors associated with the all-terrain vehicle (ATV) mortality rate in the United States, based on an analysis of state-level data. From 1990 through 1999, there were about 2400 reported deaths in the U.S. involving ATVs. The population-based mortality rate during this time period amounted to about 0.84 deaths per million persons per year, but varied considerably among the 50 states-ranging from a low of 0.09 deaths per million person-years in Rhode Island to a high of 6.33 deaths per million person-years in West Virginia. This variation provides an opportunity for quantifying some of the key factors associated with the ATV mortality risk. The analysis was conducted in a two-stage regression process, with the state mortality rates estimated in the second stage with a negative binomial regression model. The results indicate that the ATV mortality rate was systematically related to ATV usage rates (a measure of risk exposure) and a number of the characteristics of the potential rider pool. These included: the proportion of the state populations that was male, young, lived in rural areas, was college educated, and non-Hispanic white.