The most basic crime maps are a series of points (dots that represent locations of crimes or arrests), lines (showing street networks), and polygons (boundary markers for jurisdictions). The creation of maps requires more than putting data into a computer whose software translates it into a map. The creation of useful maps requires creative thinking about what data can be mapped and what data can be acquired, as well as how to obtain accurate data. There is not yet a pool of college graduates who majored in crime mapping. A department's best resource may be a rookie skilled in spatial visualization who can be trained in mapping and data analysis. Although an agency may not have the resources for engaging in sophisticated crime mapping, it should still collect and analyze data with reference to geographic regions. This should include the recording of the street addresses of houses and buildings where relevant incidents occur, which requires the standardized coding of street addresses. Global positioning systems, a recent technological advance being applied to crime mapping, can be used to place computerized pins in locations that cannot be precisely defined by addresses. Some of the uses of mapping are to show geographic trends in types of crime, areas where crime is concentrated, and areas with the most complaints against police. Other topics discussed are the selection of mapping software, organizational approaches to mapping, public access to crime mapping, mapping the location of sex offenders, fairness in mapping, and new frontiers in mapping. 8 figures