The purpose of the present study was to evaluate the professional knowledge in periodontology of the dentists, a subject which has been taught officially since 1972 as an independent area, to determine the self-assessed level of competence and to elaborate on the needs for continuing education in periodontology. The present evaluation used questionnaires sent to all members of the Swiss Society of Odontology SSO in the summer of 2000. One third of the questionnaires were returned. The questionnaires contained three parts: A) Demographic information assuring that the distribution of the answering colleagues corresponded to that of all dentists in Switzerland. B) Self-assessment of undergraduate and continuing education. Colleagues with professional experience of less than six years evaluated themselves as being most competent theoretically, while those with professional experience of 6-25 years felt most competent practically. C) Objective professional knowledge of the etiology and therapy of periodontal diseases. Such evidence-based statements had also been presented to the European Academy of Periodontology (EAP) in 1993 at the 1st European Workshop in Periodontology. In comparison to the students and faculty of the University of Washington and the EAP, it was possible to evaluate the level of knowledge in periodontology of Swiss dentists. It was evident that their professional knowledge was on a level which corresponded to the state of scientific evidence. However, there were differences between graduates from the different Swiss universities.