A small number of multi-problem, service-resistant individuals in every metropolitan community consume extraordinary amounts of human service at great cost to publicly-funded agencies with less than satisfactory benefit to the individual. This paper describes an innovative collaboration among mental health, alcohol/drug treatment, corrections, forensic, and social and housing agencies to provide more effective services at less cost. The theory of action was that (1) inter-agency communication and (2) external controls developed by core service agencies increase the efficacy of treatment and reduce the cost of caring for multi-problem clients. Agencies refer clients to the Multi-Service Network who are then screened for problematic multi-agency involvement. Case conferences result in individual service plans. Three illustrative cases are described and the results of two evaluative studies summarized. Cost of care for clients appears to have been reduced. Agencies appear to have benefited from improved information and communication. Clients' behavior was stabilized by external controls and more adequate attention to their needs.