The proper use of downsizing systems and mainframe systems was studied for the purpose of introducing, advantages of downsizing while utilizing existing information systems. Downsizing has four features: high cost performance, high flexibility and expandability, highly functional interface, and a horizontal linkage system. But compared with centralized systems, downsizing systems entail higher operation and control costs. Downsizing introduction technology has not yet been established in the field of systematization where renewal of corporate data, high security, and mass high-speed printing are required. Downsizing is suitable for fields where systematization is difficult with centralized systems, characteristics of downsizing can be fully demonstrated, and advanced and established technology is not needed. Specific examples of its application are the support of decision making, creative work, and group operation. For improving the performance of the downsizing system as a whole, its application to computers on the network, and distributed data arrangement are important. 15 refs.