By mapping past incidents of burglaries, vandalisms, and rapes, the police hope to predict and prevent similar crimes from occurring by adding police presence to neighborhoods and during the shifts that are most likely to see action. They can also use the maps to forewarn each shift of criminal activities that are likely to occur. The system uses desktop computer terminals that can obtain access to a mainframe computer through an on-line, interactive process. The system is based on ARC/INFO software from Environmental Systems Research Institute, Inc. Both systems are in the initial stages of implementation. Photographs.