The Compstat process hinges on four crime-reduction principles: accurate and timely intelligence, effective tactics, rapid deployment of personnel and resources, and relentless follow-up and assessment. Coupled with these are accountability and discretion at all levels of the agency. The Compstat facility should be large enough to accommodate all of the required personnel and also guests. The room should have audiovisual capabilities. Usually the person or unit designated to gather and collate FBI Uniform Crime Reporting and performance data handles Compstat tasks and prepares the Compstat book (a collated, printed version of the activity that occurred in the previous Compstat period). This article outlines what should be contained in the Compstat book. In displaying the data, the first step involves describing the data so that readers can quickly understand relevant information. Descriptive statistics provide commanders with a comprehensive overview of how their command is faring. Descriptive statistics portray measures of association, and they enable crime analysts to quantify the strength and direction of a relationship. These statistics enable a crime analyst to investigate crime cause and prediction. The next step involves comparing the data, which enables the chief and command staff to gauge progress and adjust or compensate for shifts in trends or patterns. Appropriate charts should display the information for each precinct as well as citywide. The final step, spatial analysis or crime mapping, identifies and plots the occurrence of crime. Crime analysts can detect "nodes," "paths," and "edges," along which criminals travel. The second part of this article, which will appear in next month's issue, will discuss the implementation and adaptability of the Compstat model. 2 figures and 10 notes