Over the last two decades there has been an increase in the number of techniques of exploratory spatial data analysis (ESDA), which can be applied in a spatial modeling environment to identify crime patterns and hotspots. This has led to the development of geographical information systems (GIS), which consist of hardware, software, data, people, and organizations for the collecting, storing, analysis, and dissemination of information relating to the earth. The field that produces these resources is known as geographic information science (GISc). The development of crime mapping stems from advances in both GIS and GISc. This article describes the application of GIS and GISc to "hotspot" mapping, i.e., the identification of geographic areas where various types of crime are concentrated; CompStat, a "goal-oriented strategic management process that uses computer technology, operational strategy, and managerial accountability to structure the manner in which a police department provides crime-control services;" and geographic profiling, which is an investigative technique designed to aid police in investigating serial crimes. The article concludes with an assessment of the status of GIS use by police agencies, noting that police managers have not generally taken full advantage of GIS in crime analysis and resource allocation. Training in GIS for police managers is discussed. 3 figures, 1 table, and 64 references