To support the evolutionary development of information systems in decentralised organisations new tools and ways of organising information systems activities are required. A communications environment which enables co-operation and co-ordination between separate sub-units of an organisation is proposed. This environment, which is called a distributed decision making (DDM) system, allows associations between groups to be built up horizontally rather than by hierarchical structuring or centralised control. The DDM system software allows separate information systems components to be developed in parallel by different groups, and provides for the linking of these applications at execution time. A prototype DDM system and experience with using this system are described. It is a flexible and low-cost approach to the development ofad hocsystems such as decision support systems.