The geographic information systems (GIS) implementation process starts with the initial decision to use a GIS; proceeds through system selection, installation, and training; and up to data-base development and product generation. This paper discusses considerations related to each phase and focuses on other facets of GIS pertinent to water-resources planning and management. Many of these considerations involve critical choices that can pose significant challenges and impose substantial costs. An understanding of these challenges can expedite the GIS implementation process. © ASCE.