The presented paper outlines a theoretical framework for professional learning that expands mainstream socio-cultural understandings of social interaction to include knowledge cultures. The weighty contributions to the field of professional development have mainly been concerned with the problem-solving capacities of practitioners and with the design of curricula, methods and instructional systems that turn them into efficient learners. Professional education, however, also has symbolic aspects, and involves the creation of images and rituals that contribute to enhance the affiliation of professional groups to knowledge cultures with high prestige. In recent reformulations of situated learning theory (Wenger, 2000) an inward turn is proposed with a greater attention to the symbolic processes that enter the formation of professional identities. Affect neutral terms like "participation", "learning" are replaced by "engagement", "alignment", and "modes of belongingness". These theories do not, however, incorporate the identification of experts with a more abstract universe of knowledge. As suggested above professional communities are aligned to both problem solving and symbolic reproduction -although contrasting values may contribute to give one aspect primacy over the other. Though there is an interplay between the knowledge base required for both tasks, they are not reducible to each other. Both forms are objects of identification and represent paradigmatic bases for the expert performance of practitioners It highlights the importance of identity formation and belonging for professional development and views knowledge cultures as partially shared meaning systems and "emotional homes" for expert selves (Knorr Cetina 1997). By focusing on the role played by abstract forms of knowledge in identity formation a model of professional learning is outlined that is more congenial to a society characterized by rapid institutional shifts and boundary crossing than suggested by the metaphor of apprenticeship. The "sensitizing value" of this frame work is exemplified by selected data from two studies that have been exploring the development of commitment structures among nurses and engineers. In the first a strategically sample of students in nursing were interviewed at different phases of their study. The key research questions were related to the formation of ties to different knowledge forms and cultures and the dominant orientation of professional education. In the second field research was conducted in an engineering and a pharmaceutical company focusing on the role of theoretical knowledge in the practice of mechanical and chemical engineers.