Background. Published work on knowledge in regional anaesthesia has focused on competence, for instance by identifying numbers of procedures required to achieve competence, or by defining criteria for successful performance of blocks. We aimed to define expertise in regional anaesthesia and examine how it is acquired. Methods. We observed anaesthetists performing 15 regional anaesthetic blocks and analysed the resulting transcripts qualitatively and in detail. Results. Expertise in regional anaesthesia encompasses technical fluency but also includes non-cognitive skills such as handling of the patient (communicating, anticipating and minimizing discomfort) and recognizing the limits of safe practice (particularly deciding when to stop trying to insert a block). Such elements may be underplayed by the experts who possess them. Focusing on a small number of regional anaesthetic procedures in detail (as is standard with such qualitative analytical approaches) has also allowed us to develop a model for the acquisition of expertise. In this model, trainees learn how to balance theoretical and practical knowledge by reflection on their clinical experiences, an iterative process which leads to the embedding of knowledge in the expert's personal repertoire of individual techniques. Conclusions. Expertise in regional anaesthesia extends beyond competence at technical performance; non-cognitive elements are also vital. Further work is needed to test our learning model, and the hypothesis that learning can be enhanced by deliberate promotion of the tacit elements of ‘expertise’ we have described.