In periods of change, psychiatric services must project outcomes of decisions about service innovations and reductions, including budgetary implications. To support such decision making, a public-sector psychiatric service in Melbourne, Victoria, Australia, developed a modeling tool that combines data from its service activity database and budgetary information with modeling techniques based on use of a spreadsheet. The model is based on clients' use of three major service components: the inpatient unit, continuing clinical care and consultancy services, and crisis assessment and treatment services. It classifies clients according to patterns of care-that is, whether they used one, two, or three of the components, in various combinations. The authors report service use and financial data derived from the model for the financial year 1992-1993. They describe two scenarios for using the model to project changes in patterns of care and costs when new services are implemented. Such a model can clarify costs, including opportunity costs, of management decisions and facilitate participation of senior clinicians in active service planning within the realities of budgetary constraints.