Health behaviors are known to be multidimensional, but the precise number of dimensions involved and their behavioral content have not been clearly established. Using convergence of factor analyses of 40 health behaviors across two samples as the criterion for identifying both the number and content of health behavior dimensions, the present study showed that individual differences in health behavior can be conceptualized in terms of a hierarchical model. At the most general level, health behaviors formed two broad categories or dimensions, preventive behavior and risk taking behavior. Preventive behavior included two empirically distinct subsets of behaviors, wellness maintenance behaviors and accident control behaviors. Risk taking behavior included subsets comprised of traffic-related risk taking and risk taking through exposure to hazardous substances. This hierarchical model is consistent with important theoretical distinctions in health behavior research, can accommodate the findings of prior studies, and should provide a useful framework for formulating research questions regarding antecedents and consequences of individual differences in health behaviors. Brief scales are proposed for use as reference measures in future studies of health behaviors. © 1990.