One of the major challenges to the integrity of individualized developmental services in community systems for the past two decades has been the assurance of timely, accessible, and high quality partial and periodic or intermittent services. For people with dual diagnosis of psychiatric and developmental conditions, this challenge is heightened by the need for conventional developmental services combined with community mental health services, in addition to social and health services. Although partial and intermittent service approaches are intended, generally, to be conducive to supportive living and compatible with group home living, in fact these goals have not been readily achieved.This volume represents the interactionist position that has become more common in service design and development today. It is our hope that the dissemination of effective models of services and support for people with dual diagnoses, such as those presented in this volume, will accelerate the development of sufficient partial services for people with dual diagnoses. As pioneering efforts in organizing partial dual diagnosis service provision, some of the models presented are still in development, and it is hoped that their breadth and scope will inspire programmatic and evaluative innovation.