The Dallas Police Department started using computer systems in the late 1960's and kept expanding and upgrading them in subsequent years. However, it did almost no planning regarding its long-term needs. The result is a system that is fragmented, often overwhelming to users, and frequently in need of revision. The department's experience underscores the necessity of extensive planning regarding computer needs over the long term. This planning must take into account the police department's interactions with other parts of the criminal justice system and account for the needs of prosecutors and others. Police agencies must also recognize the limitations of centralized data processing systems and should develop a system that has both centralized and decentralized components. Police agencies should also analyze costs over time and should be aware that data base systems have major operating advantages over systems based on files. Finally, they should be informed about technological developments and should not limit their research and planning to what is already available. Basing all their decisions on a detailed, long-term plan will enable agencies to make day-to-day decisions that will move them toward their goal.