When a child is diagnosed with cancer, his or her entire family is affected. Parents are shocked and devastated when they learn of the cancer diagnosis and soon after diagnosis are responsible for making difficult treatment decisions that may cause their child pain and fear. Siblings may witness the physical and emotional pain of their brother or sister and their parents and experience sudden, extended separations from them. Family roles and responsibilities shift to accommodate cancer treatment and to attend to the needs of the ill child. These new demands must be balanced with the family’s previous dynamics and their implicit goals of fostering growth and development within the family. Furthermore, the reactions of individual family members have an impact on each other and can influence the way in which the child approaches cancer treatment (i.e., procedure-related distress and adherence). The purpose of this chapter is to discuss issues pertinent to the family when a child is on treatment for cancer. Like all childhood illnesses, childhood cancers occur within a complex network of social systems, such as health care, school/peers, and the family (Kazak, Rourke, & Crump, 2003). A helpful framework for conceptualizing the important social contexts that influence and are influenced by a developing child is the social ecology model (Bronfrenbrenner, 1977). This model proposes that the child is at the center of many nested social systems, typically depicted as a series of concentric circles surrounding the child. Large macrosystems such as culture and societal values comprise the outermost circle, and smaller, more immediate microsystems such as the family, neighborhood, and school are depicted nearer to the child. Although all of these systems are important in the development of a child and useful for understanding adaptation of children with chronic illnesses (Kazak, 1989; Kazak & Christakis, 1996), the most important and immediate social system that involves the child is his or her family. Our most basic conceptualizations of the ways in which families work stem from biologically based general systems theory (Engle, 1980; von Bertalanffy, 1968). Systems theory is inherently integrative and complex and highlights principles of organization and interrelatedness.