The establishment of a good rapport between dentist and patient is together with providing information a basic prerequisite for successfully motivating the patient to comply with the guidance the dentist provides. Both the style adopted in verbally communicating with the patient and also nonverbal communication play a decisive role in the establishment and maintenance of such a relationship. In the pilot study presented here, which draws on psychological interaction analysis of video recordings taken of the initial consultation with 27 patients and of 28 routine treatment sessions with different patients, the typical interaction patterns between the orthodontist and the patient are objectively assessed and compared. The most important findings of the study were: (1) The mean duration of the chairside sessions was lowest during routine encounters with cooperative patients. (2) During consultations approximately 2/3 of the time was taken up talking to each other. On the other hand, in treatment sessions with uncooperative patients only 1/4 of the time was devoted to verbal communication. (3) The orthodontist dominated the conversation in all groups and especially in conversing with the uncooperative patients. (4) In the consultation sessions the dentist and the patient related relatively strongly to each other. (5) Providing mere information significantly predominated over any discussion of the professional aspects of the treatment. (6) During the consultations eye contact was maintained over almost all of the sessions.(ABSTRACT TRUNCATED AT 250 WORDS)