A comparison is made between two alternatives for explaining family size decisions: a psychological model based on the individual utilities of the spouses and a social psychological model based on the husband-wife relationship. By use of higher order factors within the context of structural equation models, it is shown that the two approaches can be derived as special cases of a single, integrative framework. In this way, a theory is developed and tested which explicitly represents the family-size decision process as both an individual and joint experience of the spouses.