Phenylketonuria (PKU) is estimated to occur in 1 in 8,000 to 20,000 live births. Newborn screening identifies these children and proper dietary management changes the course of their lives from mental retardation to normal intelligence. However, there are many factors that influence whether the family and the person with PKU will cope satisfactorily with this lifelong condition. Interdisciplinary teams often assist the family and client with this process. As a member of the team the nurse assumes a counseling and teaching role. That role, following a developmental perspective, is presented in this article.