As regulations change regarding the operation of wastewater collection systems, understanding system performance relative to infiltration/inflow (I/I) is a key issue in the development of a collection system master plan. This paper describes how GIS can be used to effectively integrate hydraulic modeling, inspection, and asset data to evaluate potential collection system improvements. Included are specific examples of how ArcView GIS and MapObjects can be used to view and relate various data sets as well as perform spatial analyses to gain a better understanding of a wastewater collection system's performance.