A description of the methodology developed in the course of a five-state longitudinal study, based on administrative data from the child care subsidy program, on the dynamics of child care subsidy use--including characteristics of children and families who receive subsidies, services received, length of subsidy receipt spells, probability of reentry into the subsidy system, and stability of children's care arrangements while they are in the subsidy system--designed as a guide to enable states and researchers to conduct similar studies on this topic