 The studys goal is to evaluate whether home treatment is an effective and efficient alternative to inpatient care for people with acute mental illness. Therefore, psychiatric patients in need of hospitalization who meet the studys inclusion criteria are randomly assigned to either the condition home treatment or inpatient care treatment-as-usual during one year. Home treatment patients are visited by a mobile and multiprofessional care team at their homes. Additionally, patients without a health insurance for home treatment and patients who are directly assigned to home treatment are included in separate study groups. Following two years, it will be checked whether home treatment leads to a reduction of inpatient days as a primary outcome. Further outcomes such as cost effectiveness, rehospitalization rate, severity of symptoms and sociodemographics will be also analyzed. 