The German Society for Psychiatry, Psychotherapy and Neurology (DGPPN) guidelines on psychosocial interventions for people with severe mental illness appraise the transferability of results of trials evaluating community-based mental health services to the German situation. This assessment has to draw on research results on factors determining effectiveness. This must be seen against the background of a lack of high-quality trials in Germany. The article discusses system, context and setting factors related to the transfer of evidence on community-based service models from other countries. These issues are discussed on the basis of evidence concerning the models of case management, assertive community treatment and community mental health teams. International differences in study findings are highlighted and the importance of treatment-as-usual in influencing study results is emphasized. The more control services including elements of community-based care there are and the less the pressure to reduce inpatient treatment (threshold to inpatient care admission), the smaller the relative effect sizes of innovative care models will be.In the absence of direct evidence, careful examination of transferability is required before introducing health care models. Research has revealed solid evidence for several factors influencing the effects of innovative community mental health care. Among key factors in the care of people with severe mental illness, home visits and joint team responsibility for both psychiatric and social care were identified. This evidence can facilitate the adaptation of successful mental health care models in Germany.