"Professions" are work collaborations in which representatives of certain vocations address the life problems of "laypersons." In such relationships, adequate communication between representatives of the profession and laypersons is crucial in addressing their individual problems. Accordingly, "understanding," as well as interactional documentation of this understanding, is of considerable importance. The authors of the present volume, "Understanding in Professional Spheres of Activity," address the documentation of this understanding in certain professional spheres. They examine the requirements for the documentation of such understanding and the forms of documentation used in the fields of doctor-patient communication, counseling communication, and organizational collaboration on a movie set. Conversation analytic as well as ethnographically complemented studies draw further attention to an examination of the interactional level in its socio-structural context, and to that end the study employs a combination of conversational linguistics and sociological research. This contribution is therefore important not only in terms of linguistics but also sociologically.