Although not often included in the literature devoted to exclusionary zoning practices, an examination of the use and abuse of family definitions in American municipal zoning ordinances is important to those who are concerned with the revitalization of American cities and suburbs. Many of the ideas suggested for innovative reuse of existing housing are linked to the family definition. Accessory units in single‐family dwellings and shared housing are two examples. This paper briefly examines the history of family definitions in municipal zoning ordinances, reviews the major court decisions concerning their use and discusses the relevance of the continued use of family definitions when current demographic changes are taken into consideratio