Victimization studies consistently find that household structure influences the risk of personal and property victimization among adult household members, with those in "traditional" homes enjoying the most protection from victimization and lone parents experiencing the greatest vulnerability. Drawing on the concept of "coupling constraints," which represents space-time limitations on adults' routine activities, this study builds upon and extends research on the household structure--victimization relationship by considering how the presence and age of children shapes adult victimization risk. Data from 11,952 urban respondents in the Canadian General Social Survey (1999) confirm that adults' life course stage, captured in age-graded responsibilities to children, has an independent and direct influence on nonpartner victimization. The heightened victimization risk experienced by lone parents relative to other types of households is largely explained by their parental coupling constraints. (Contains 2 tables and 2 notes.)