This article presents the cross training program in Montreal's south-west. The authors underline that the context of post-deinstitutionalization and mental health service integration impose new roles to professionals who work within these different networks of services. Cross training thus appears as a model that is particularly adapted to their needs in order to optimize their interventions. The model is presented with a review of the most recent studies and is illustrated with the cross training program, a model developed by the networks of mental health care and addiction treatment in Montreal's south-west. The program's applications are examined for other networks of care and services.