Distributed systems has been an area of intense activity over the past ten years. The subject is entering a stage of maturity with work now focusing on standards for open distributed processing (ODP). Recently, however, a number of new challenges have emerged for distributed systems. Among these challenges, distributed systems are increasingly having to support multimedia services, and this has raised a number of issues for distributed systems designers. One of the most important issues in this area is that of synchronization. Multimedia applications require sophisticated support for synchronization both to coordinate multimedia presentations and to maintain timing relationships between a number of real-time data transmissions. Current distributed system architectures do not support such services. The paper discusses the problem of incorporating support for synchronization in open distributed system architectures. It is argued that support must be provided for synchronization both in the invocation mechanism and in the form of new services called streams and synchronization managers. The proposals are compared to related work in the field.