In order to describe clearly and undoubtfully each psychotherapeutic situation, combining one or several therapists in one or several psychotherapeutic methods, an original classification is proposed. Evolution of concepts such as co-psychotherapy and multiple psychotherapy are studied. Advantages and disadvantages for both therapist and patient are listed, and generally accepted viewpoints as well as controversies are discussed. A statistical survey, using a large number of undifferentiated registrations made by a representative number of psychotherapeutic teams, permits a first approach of the present situation in this particular field of psychotherapy, and some significant conclusions are to be made.