This thesis is concerned with the provision of multimedia services (involving voice, video, text and graphics) in an office environment. The office of the future is expected to comprise a heterogeneous collection of workstations and multimedia components (including fileservers, voice and video codecs, document scanners, laser printers, etc) interlinked by a high speed (digital) local area network. Every office is likely to have one or more connections to a public Integrated Services Digital Network (ISDN) providing integrated access (involving various types of traffic) to a very large number of subscribers. This thesis considers general issues relating to the design of such an office. Particular attention is given to the problem of the integration of media both at the network and user levels. Much of this discussion draws on practical experience gained during the Alvey Unison Project in which experimental multimedia offices were interconnected using a pilot ISDN. The architecture of the Unison network is discussed with particular reference to its suitability for the support of multimedia services. The bulk of this thesis is devoted to a description of the design and implementation of a number of prototype multimedia applications, and to an evaluation of their performance over the network. The handling of slow-scan video and high resolution images have been particular areas 01 interest. Much emphasis is placed on the problem of control in a distributed environment, and a model is presented for the management of control based on the use of a directory-like service. This model also provides a mechanism for locating an office service based on the name of the user to whom it belongs.