Taurodontism is a morphologic dental trait showing continuous expressivity, and criteria of the degree of pulp chamber elongation vary in different investigations. The aim of this investigation was to test a simple method of assessing taurodontism in the developing dentition from orthopantomograms in order to determine its reliability for later use in epidemiologic investigations. The method was also compared with other methods. Forty-three children 10-16.9 yr of age with one or more taurodontic permanent first or second molars were selected for the study. A subgroup of 16 children with two longitudinally obtained radiographs was used in a follow-up study of the same tooth in two different formational stages. The follow-up time averaged 2.2 yr. The distance between the baseline connecting the mesial and distal points of the cementoenamel junction and the highest point of the floor of the pulp chamber was measured (Measure 3). A tooth was classified as taurodontic when Measure 3 reached or exceeded 3.5 mm. This distance remained unchanged during the course of tooth development. Intraexaminer reliability of two examiners in reproducing the same classification was, on average, 96.2%, and the interexaminer reliability was 93.2%. The reliability was greater for the first than for the second molars. Results obtained by this method agreed well with those obtained by other methods. Measure 3 proved to be reliable in assessing taurodontism in the developing dentition from orthopantomograms in epidemiologic investigations.