Abstract-This review describes Assertive community treatment (ACT), an integral component of the care of persons with severe mental illness. Drawing on research from North America, Australasia, and Britain, we summarize the current evidence base for ACT and examine the trends and issues that may affect practice. Strong evidence supports the fidelity standardization, efficacy, effectiveness, and cost-effectiveness of ACT models in psychiatry. Yet, significant methodological problems and issues affect implementation. The evidence indicates that the ACT model is one of the most effective systematic models for organizing clinical and functional interventions in psychiatry. Effective systems based on the ACT model meet more ACT fidelity criteria; are often noncoercive; do not rely on compulsory orders; may rely on a wider range of interventions than just medication adherence, including vocational and substance abuse rehabilitation; contain other evidence-based interventions and more mobile in vivo interventions; involve individual and team case management; may involve consumers as direct service providers; and have an interdisciplinary workforce and support structure within the team, providing some protection from work-related stress or burnout.