This research analyzes the process used to evaluate potential relocation sites for Army Reserve units from the perspective of military readiness. A comparative decision model (based upon Multi-Attribute Utility Theory), augmented by a Geographic Information System (GIS), was designed and implemented in an automated Spatial Decision Support System (SDSS). This SDSS provides a flexible structure that can be generalized to serve as an executable conceptual model for a wide range of decisions containing significant geographic or location related components. The Army Reserve Installation Evaluation System (ARIES) integrates several commercial software products in a seamless and synergistic manner. Data extracted from numerous large databases is spatially processed by a commercial mapping engine, and then overlaid onto a formal decision model. The decision maker can rely on a single, simplified interface that consistently applies the professional judgement of a panel of experts to produce standardized reports, or choose from a robust suite of methods for model management, sensitivity analysis, and the display of results. A process that previously required weeks can now be completed in minutes. More important, this approach improves the decision maker's effectiveness by conveniently providing insights into the nature of the source data and the decision process.