This paper summarises the findings of a research project on interprofessional collaboration in the emergency unit of a major Finnish hospital. The findings are discussed through a broad conceptual framework which involves work process knowledge and interprofessional collaboration. The project, carried out from 2010-2012, investigated different forms of, prerequisites for, and barriers to, collaboration, and the aim was to develop the work together with staff at the unit. An ethnographically informed research strategy was utilised, with observations and interviews as the main data collection methods. On the whole, collaboration in the emergency unit was found to function rather well; i.e. patients receive good-quality treatment within the ideal time frame. We found that in the unit, the most suitable form for the majority of collaborations is multi-professional collaboration, in which professionals exchange information but still adhere strongly to their own professional groups. More interprofessional collaboration is required particularly in leadership and management, to create further improvements in (1) the coordination of work as a whole, and (2) the implementation of organisational changes and new professional roles. Obstacles to interprofessional collaboration in particular appear to be: (1) diverging professional values and core professional identities, and (2) power relations that create inequality.