Critical Time Intervention (CTI) is designed to prevent recurrent homelessness among persons with severe mental illness by enhancing continuity of care during the transition from institutional to community living. After providing the background and rationale of CTI, we describe the elements of the model and summarize the status of existing research on its effectiveness. We then briefly illustrate how the CTI model has begun to be adapted and implemented by providing a case example of a homeless woman's transition from shelter to housing. Finally, we consider plans for the further adaptation, testing and dissemination of CTI in other populations and service delivery settings.