As health care companies battle for market share in a competitive marketplace, planners need new ways to identify the makeup of the battlefield. GIS software helps planners identify physician locations and affinity groups to help create the right alliances. Mapsco helped System Health Providers (SHP), an affiliate of Presbyterian Hospital in Dallas, do that. Mapsco geocoded SHP's physician database, then used fields in it as selection criteria separating physicians into analysis categories. Then we prepared maps for the planning process. While the planners "knew" intuitively the makeup of their marketplace, the maps focus on specific groupings to help make better decisions.