Obtaining data suitable for analysis is complicated: although demographic data are collected regularly by a number of agencies and are readily accessible, the data collected may not suit the purposes of particular analyses (e.g., of rape victims or elderly crime victims). For optimum usefulness, demographic data must be combined with other crime data since a combination of information on the community and on community crime may be essential to assessing the difficulty of implementing community action programs. Maps may be prepared to slant the data presentation or to relate particular crime areas to particular groups in a comprehensible manner. The most common types of maps illustrated here are concentration maps, distribution maps, and unit share maps; each type has a different visual effect in presenting similar data. Spacial aggregates permit combination of variables to be used either by the police or for planning purposes. Such aggregates may be classical longitudinal/latitudinal grids, block systems, or address coding grids such as the ZIP code system. A computerized system (such as the Dual Independent Mapping Code) may be useful for updating maps and grids, but for small areas manual techniques are easier to use. When problems arise in obtaining some types of data, equations can be used to create new data from existing data without the trouble and expense of a survey. The 'symbiomap' is shown to illustrate the most advanced forms of representing data spatially, and the availability of LEAA software to combine different types of data is noted. The speaker is the Senior Research Associate for the Program for Data Research at the University of Southern California's Social Science Research Institute.