Defining Issue: The primary tool used to measure property appraisal performance is the ratio study. When sales ratios are put into a spatial perspective, it adds a new dimension to the data. Areas of anomaly (outliers) are spotted on the map and patterns can be established. GIS Solution: Using appraisal data (Oracle) and cadastral maps (ArcInfo), the author created a model to visualize a sales ratio study in ArcView GIS. This paper focuses on the methodology and applications of the process. Included is a case example of using a GIS presentation at a property value-adjustment board hearing.