This article reports on selected findings from an action research study that looked at the lessons learnt from setting up a new in-patient stroke service in a London teaching hospital. Key participants in the design and evaluation of this 2-year study included members of the multi-professional stroke team and support staff within the unit, the hospital management team and representatives of patients and carers. Mixed methods (focus groups, indepth interviews, audits, documentary analysis, participant observation field notes) were used to generate data. Findings demonstrated positive change over time with four main themes emerging from the process: building a team; developing practice-based knowledge and skills in stroke; valuing the central role of the nurse in stroke care; and creating an organisational climate for supporting change. The interplay of these non-linear, but interrelated factors is supported by complexity theory, which includes exploration of how the sum of a whole can be more than its constituent parts. Findings are likely to be of interest to practitioners, managers and policy makers interested in supporting change in a learning organisation. (Contains 2 tables, 2 figures and 1 note.)