Researchers and policymakers often suggest that housing instability harms well-being across multiple domains. But housing instability can be operationalized in various ways, and whether all forms are equally detrimental—and whether each form causes disadvantage or merely reflects it—is unknown. Using National Longitudinal Survey of Youth 1997 data, the authors advance theoretical and empirical understandings of housing instability in three ways. First, they document the prevalence and (lack of) overlap between multiple dimensions of instability. Second, using methods that carefully attend to selection, the authors investigate which forms of instability appear to affect employment, health, and family structure. Finally, they investigate disparities by race/ethnicity, gender, and class background. The findings are mixed. Some forms of instability appear consequential for some outcomes, but not all. The authors find some variation by race/ethnicity, gender, and class. They conclude that housing instability may be a mechanism of inequality, but not one that can be treated as monolithic.