MPEG4 is a natural extension of audiovisual coding, and yet from many perspectives breaks new ground as a standard. New coding techniques are being introduced, of course, but they will work on new data structures. The standard itself has a new architecture, and will use a new operational model when implemented on equipment that is likely to have innovative system architecture. The author introduces the background developments in technology and applications that are driving or enabling the standard, introduces the focus of MPEG4, and enumerates the new functionalities to be supported. Key applications in interactive TV and heterogeneous environments are discussed. The architecture of MPEG4 is described, followed by a discussion of the multiphase MPEG4 communication scenarios, and issues of practical implementation of MPEG4 terminals. The paper concludes with a description of the MPEG4 workplan. In summary, MPEG4 has two fundamental attributes. First, it is the coding of audiovisual objects, which may be natural or synthetic data in two or three dimensions. Second, the heart of MPEG4 is its syntax: the MPEG4 Syntactic Descriptive Language—MSDL.