Organisations spend a great deal of efforts on information management, but if they are not successful in information mediation and use, it can be a waste of resources. In this paper we have applied a knowledge perspective on mediation and use. The purpose is to describe and explain why knowledge integration processes in knowledge-intensive routine work may work or fail. As an example of such work we have used a case study from the Swedish healthcare sector, more specifically a microbiology laboratory and some of its customers. Empirical data were collected by interviews and observations, and analysed with the help of theories about knowledge boundaries, knowledge integration and knowledge mediators (boundary objects and brokers). The case analysis shows that the boundaries between these groups are more complicated than they may appear to be at first sight, but also that there are methods to create a common understanding and overcome the complications. The main conclusion is that in this type of work, there are in fact several different boundaries between groups, depending on differences in work tasks, interest and motivation and that various ways to attain knowledge integration, directed both to groups and to individuals, can be required.