Childhood chronic illness is the presence of a health condition, in an individual under the age of 18, that has a measureable negative affect on the child’s functioning, and that is not expected to improve or be cured over an extended period of time. This entry discusses the characteristics and implications of childhood chronic illness, with particular attention to the reciprocal relationship between the course of the illness and family functioning. The entry concludes with an overview of some of the considerations that should be undertaken when providing family therapy to this population.