In this paper it is our intention to discuss a Teacher Education proposal that uses an on line asynchronous learning environment to develop collaborative practices and to enhance a professional identity. Using an integrated multi-method approach for analysing the on line discussions of 47 student-teachers, a research group of the University of Padua has explored: a) how different groups of student-teachers build and modify their professional profile pre-post a case-work on line activity; b) the nature of the interactive processes activated during case-work on line activity; c) the styles of case solutions. The findings show that the collaborative learning context supported pre-service and in-service groups of students differently in their professional development and in professional identity changes. Some implications for future research on teacher education are discussed.