This thesis looked inside the black box of stroke care, so called because its contents are not clearly defined. This case study of success illustrated how a new inpatient stroke unit (SU) was created in an inner London teaching hospital, transforming treatment for patients with stroke. Whilst it is known that good stroke care results in improved patient outcomes, it is not fully understood how or why. As stroke is the second major cause of death in adults worldwide, and a leading cause of adult disability in the UK, it is essential more is known about how evidence translates into practical knowledge for use in mainstream practice. This action research study, through the systematic documentation and evaluation of the processes and outcomes, has unpacked and illuminated factors that enabled development of success, and provides the first empirical account of its kind. This study adds to the knowledge of knowing how. A variety of qualitative and quantitative methods were used to generate data between January 2001 and November 2002. Findings were analysed using Immersion I Crystallization and descriptive statistics. When the black box of stroke unit care was opened, four key interrelated themes emerged from the process findings: building a multidisciplinary stroke 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 improvement. Analyses of findings suggest the creation of excellence in stroke care was linked to the development of a Community of Practice (CoP), which combines three elements; domain, community and practice, into a conceptual framework of learning that fundamentally places the acquisition of knowledge into a social process of learning. Whilst improvement initiatives have recently been linked in the literature to CoPs, no guidance is available on how this should be done. This thesis makes an original contribution to the body of knowledge by providing the first empirical evidence of not only on how a CoP was created, but shows how it developed into a functional multidisciplinary CoP, a concept identified in the literature as difficult to accomplish. In concluding, issues related to practice, research, education and policy are raised for future considerations.