The problem with the capacity-based operational definitions of prison crowding is that they do not adequately represent the conceptualization of the phenomenon and cannot be used to make meaningful comparisons across institutions or across time. These types of comparisons are needed to give direction to both research and policy making. In the process of refining, revising, and explicating a final multidimensional additive model of jail crowding, the focus group discussed several elements of the model including number of inmates and jail capacity, timing issues, intake fluctuations, composition of inmates in the population, characteristics of the jail, disruption of jail operations, management issues, and relations with outside agencies. This elaboration of a model of crowding is one step toward the development of an index of severity for jail crowding. 1 figure and 40 references (Author abstract modified)