A theoretical framework linking defensible-space theory with an opportunity model of predatory criminal victimization suggests that structural density has a positive relationship with victimization, independent of victim characteristics. This perspective is compared to recent empirical and theoretical works that argue that density has either no relationship or an inverse relationship to crime. Hypotheses are tested with National Crime Survey victimization data for the years 1973 to 1978. The results support the major hypothesis and show that structural density is positively related to rates of robbery and assault victimization, controlling for age, race, and sex of victim, and for extent of urbanization. Surprisingly, the positive relationship between structural density and victimization is stronger in rural areas than in urban areas. (Publisher abstract)