This paper describes the implementation types of private networks from the viewpoint of equipment and users, and utilization trends from low to high-speed services. Technology trends of private networks from the viewpoint of high-speed and broadband communication, multimedia communication, media access methods and intelligent communication are also examined. A concept for implementing future private networks in the Broadband ISDN (B-ISDN) age, and the major technology and the future efforts to achieve this implementation are discussed. Asynchronous Transfer Mode (ATM) is shown to be the key technology for integrating both various and heavy traffic media communication.