The current status of an 8-year project to develop an advanced Man-Machine System for Nuclear Power Plants (MMS-NPP), started in 1984 through support of the Japanese Ministry of International Trade and Industry (MITI), is summarized. AI techniques and multi-media communication technologies are being applied to MMS-NPP in order to provide enhanced performance of the operation support functions; for planning and monitoring plant operation under normal conditions; maintenance work planning; anomaly and accident management; and intelligent man-machine interface matching operator's cognitive processes. The fundamental paradigms for the support functions are confirmed through case studies by off-line simulation tests.