Inpatient hospital units (IU), partial hospital (PH) or day treatment (DT) programs, and residential treatment centers (RTCs) (sometimes grouped as "restrictive" or "intensive" services) play a critical role for children and adolescents (youth) with severe and/or persistent mental illness requiring extensive or intensive health and psychiatric services. Federal reports sometimes combine residential and inpatient statistics, while PH/DT is now pooled with outpatient treatments. A common set of values and expectations allows these programs to be considered together. A therapeutic milieu is central to each. This chapter describes common features across these milieu treatments (MTs) and considers each modality by defining the intervention and describing its structure, clinical role, and related issues.