The concept of identity has gained currency in recent literature on professional learning. However it tends to neglect the role of knowledge in both identity formation and learning processes (Lahn, 2006). For members of professional communities and their associations issues related to their knowledge domain are of strategic importance since it defines what they are and what they are entitled to do. Such an identification is both more critical and challenging as production processes are becoming increasingly knowledge-dependent (epistemification) and object-mediated through the pervasiveness of webbased technologies and systems. These characteristics are included in Karin Knorr-Cetina's (1997) concept "epistemic culture" that we want to lean on as an overall theoretical perspective for our comparative study of professional groups. It addresses the following questions: In what situations do professionals access knowledge? How is this process mediated by different types of artefacts and personal networks? How does these settings afford problem-solving and learning?Since Knorr Cetina's definitions of "epistemic culture" are processual, we have used the code-model of Basil Bernstein (1996) to develop three structural dimensions: Classification of expert domains, turnover of professional knowledge and formalization of training. Departing from these distinctions we develop an "epistemic profile" for each of four professions: Accountants, computer engineers, nurses and teachers. The profiles are analytically linked to our main data on "dynamic affordances" (Cook & Brown, 1999) in professional work. In our operationalization of this concept we have focused on the element of deliberation during the work day, the type of knowledge mediation and the potential for learning through the practitioners' elaboration of knowledge resourcesThe data for this paper is taken from the national project "Professional learning in a changing working life" (ProLearn, see www.pfi.uio.no/prolearn) that includes both a survey study that followed students in accounting, computer engineering, nursing and teaching during their study and into their professional life (follow-up two and four years after graduation). A subset in each group was selected for semi-structured interviews and learning logs. The analyses presented in this paper are primarily based on the learning logs. These were constructed as short questionnaires without precoded categories for answers - to be filled in during four days in two one-week periods. A total of 138 work days was summarised in the logs. The data shows that the accountants and engineers described their domain as strongly classified whereas the nurses and teachers sew a less circumscribed structure. All groups except the engineers expected slow and small transformations in their professional knowledge base. They reported widely different regimes for up-dating of skills - from informal on-the-screen training for computer engineers to formalized schemes in accounting and nursing. Our learning logs indicate that novice professionals regularly encounter new problems in their jobs. They differ in their framing and the use of knowledge sources in handling non-routine tasks (evaluative use for accountants, informative use for engineers, explanatory use for nurses and reflective use for teachers). Also a variety of argumentative practices is demonstrated though their reports - providing different contexts for learning processes in professional work.Bernstein, B. (1996) Pedagogy, symbolic control and identity. Theory, research, critique. Lanham: Rowman & Littlefield Publ. Cook.S.N. & Brown, J.S. 1999. Bridging epistemologies: The generative dance between organizational knowledge and organizational knowing. Organization Science 10 (4), 381-400. Knorr-Cetina, K. (1999) Epistemic Cultures. How the Sciences Make Knowledge. Cambridge, Mass.: Harvard University Press Lahn, L. C. (2006) Professional learning as epistemic trajectories EARLI SIG Professional development and learning;Heerlen 11.10.2006 - 13.10.2006. European or international journal