A survey covering 8 years and 3350 consecutive endodontic patients (1958 men (58%) and 1392 women (42%)) was conducted to determine the frequency of endodontic treatment for each tooth. At the time of initial examination, 3672 teeth required root canal therapy. Three hundred twenty-two patients needed endodontic therapy on multiple teeth. Posterior teeth were most frequently treated, 80.1% of the total with molars requiring 52.6% of the needed endodontic treatment. The mandibular first molar was treated most often, 18.8% of the time, followed by the maxillary first molar (13.5%) and the mandibular second molar (12.0%). The number of endodontically treated maxillary and mandibular teeth was similar, 50.8% and 49.2%, respectively.