The past decade has witnessed increased research emphasis on children's developing conceptions of their social environment. In the present study, 64 children in grades 1 through 6 were interviewed to examine age-related changes in their understanding of the concept of family. The study also explored whether children's developing conceptions of the family were mediated by their own family structures. Results indicated five levels of family concept understanding that reflected a growing (i.e., age-related) facility in children's application of kinship criteria across traditional and nontraditional family groupings. However, the sophistication of children's understanding of the family was not related to the structure of their own families. These findings suggest that children's level of cognitive development is more important for their comprehension of the family than the specific experiences derived from living within their own unique family. Implications of these findings for mental health professionals who work with families in transition are discussed.