Examining in particular the impact of fostering on birth children, this article reviews the literature on the needs of birth children of foster parents. Among the findings are that the behavior and emotional difficulties of the foster child, and the difficulties between foster children and birth children in one family are two factors that influence foster placement stability. There is a negative relationship between birth children and placement stability in foster homes. Fostering places four stresses on a foster family: disruption of family equilibrium; coping with a child in transition; dealing with an alien agency; and harboring great expectations. Dealing with troubled children requires special skills. Based on the literature review, it is recommended that foster children be carefully matched to the foster family, that the birth children of foster families be prepared for fostering, and that the whole family be trained and helped to understand their role in foster care delivery. It is also suggested that because the literature on foster family birth children's needs is scarce, more research in this area is needed. (AS)