The papers in this special issue of the Journal of Quantitative Criminology focus on lifestyle or routine activity theories of crime. Most examine victimization, although two authors apply the lifestyle perspective to offending. The general nature of this evolving body of theory will be familiar to most readers. But for the record, and for the benefit of those less familiar, this introductory essay briefly discusses the meaning of lifestyle and routine activity theories and sets the stage for the substantive contribu tions. Readers interested in an exhaustive and definitive exposition or in a detailed critique of various formulations and tests of lifestyle theories will have to look elsewhere [see Garofalo (1987) for an excellent summary]. What people do, how they behave, places them at more or less risk of criminal victimization. Stated so directly this seems like little more than common sense. In much the same way, routine behavior "explains" how people avoid or suffer many other misfortunes. Careful drivers are at less risk of auto accidents, careless smokers stand a greater chance of setting fire to the house, coal miners suffer disproportionately from pulmonary disease, and mariners are more likely to drown than, say, mountain climbers. The next section tries to impose some order on the various names and terms that have attached themselves to the lifestyle theory of personal victimization developed by Hindelang et al. (1978). Discussion then turns to certain themes that have emerged in previous empirical studies. The final section describes how the papers presented in this issue contribute to lifestyle theory and introduces James Lynch's concept of activity domains.