The term day hospital denotes a type of service that is intermediate in level of intensity between impatient and outpatient care. It is generally conceived as a less expensive and less restrictive alternative to impatient treatment, yet one that provides many of the same services that are available in the hospital. While the words "day hospital" are often used interchangeably with "partial hospital," a day hospital is a specific type of partial hospital program, in which patients attend for several hours during the day, returning to their homes in the evening. Partial hospitalization, a broader concept, encompasses after school and evening programs, as well as the "inn" for adult patients. This chapter uses both terms to refer to the definition that follows developed for partial hospitalization for children.