This article considers non-unitary models of household behavior. These models suppose explicitly that households consist of a number of different members with preferences that are different from each other. They can be split up into two principal categories: cooperative (or collective) models, in which the allocations are supposed to be Pareto efficient; and non-cooperative (or strategic) models which are based on the concept of Cournot-Nash equilibrium. The demand functions that describe household behavior in these models are subject to constraints that differ from the traditional Slutsky conditions. In addition, in a certain number of specific cases, the preferences of the different household members can be identified from observable behavior.