In this thesis I shall present the argument that intranets increase the role of ambiguity – confrontation between contradicting frames of interpretation – in organisational communication by encouraging processes across organisational borders. In the first chapter I discuss philosophical aspects of ambiguity and interpretation. Based on the ideal of rationality I emphasize the ‘challenges’ of ambiguity, which is inhibitive to rational processes, but also holds a potential for a rational and universalising resolution. In the second chapter I identify the role of ambiguity in organisations. Ambiguity increases with tendencies to cooperate and communicate across organisational boundaries, mainly as a reaction to developments in markets and industrial knowledge base, but also due to the potential provided by computer network. In the third chapter I identify some characteristics of two fundamental intranet media, email and the web, partly in the perspective of media richness theory, partly compared with philosophical discussions of classical media. The fourth chapter presents an intranet in a global company, in which problems and challenges related to ambiguity have proven significant.