The panel presents possibilities and challenges of a multidisciplinary and inter domain approach, applying Behavior Analysis to two nationally renowned public hospitals in Brazil. Three different applications are shown, at three different units and faculties at the largest University in South America (USP), inside and outside it, with professionals coming from diverse organizations. It involves, mainly, two different domains of Behavior Analysis: applied research and service delivery, all of them in the context of a partnership between public university, public hospital and private initiatives. It involves different disciplines: psychology, psychiatry, art, nursing and education, with the common context of Behavior Analysis. It describes and discusses three different approaches: 1) a program of creating a behavioral environment at a Children Ward, at the Psychiatry Institute; 2) a research on the process of adults behavior change during one year of Behavioral Therapy at a University Hospital; 3) a parent training program for those parents at the Children Ward and for those at the Daily Hospital Program. Results shows: 1) pivotal changes in the behavior of the nursery staff, related to the knowledge and application of Behavior Analysis; decreased in the organizational indexes of contention due to aggressive behavior of children; 2) positive correlation between progresses in the behavior of clients and points in psychiatry and social scales; 3) changes in the parents behavior in the direction of a more positive reinforcing contingencies. Considering the involvement of different disciplines and professionals originated from different organizations, discussion will be conducted in the light of the possibilities and challenges of a multidisciplinary and inter domain approach application of Behavior Analysis.