York Behaviour Management Services, one of 33 programs funded by the Ontario (Canada) Ministry of Community and Social Services, is designed to help deinstitutionalized handicapped persons adapt to the demands of community life. An introduction (presented by D. Griffiths) on the background of behavior modification reviews reasons for some negative attitudes toward the approach. The management system advocated in the paper differs from some previous applications in that service is provided in the client's normal environment, and help is also provided to critical support persons in the environment. Further discussion of the model centers on its application to transitional planning for deinstitutionalization (presented by Linda Hickey); services (focusing on prevention) offered to parents, teachers, direct care staff and other mediators in the community (presented by Lynann Outram); and a preventive orientation to serious behavior problems (presented by Andrew J. R. Harris). (CL)