Abstract
This paper introduces the Special Symposium Issue on the Assimilation of Problematic Experiences and on the Assimilation Model. The main context of these studies is the process research trend in psychotherapy. Process research keeps a direct connection with outcome research and it tries to explore (in many different ways) how patients and therapists are involved and related in therapy and what kind of therapeutic activities, operations or variables are influencing the therapeutic change. In this process context qualitative studies are contributing greatly to give a more detailed explanation of the process of change. The Assimilation Scale and the Model developed by Stiles and his group are embbeded in this qualitative stance. So, in this introduction some of the main concepts and theoretical foundations of the Assimilation Model will be addressed as well the main conclusions of the papers edited.