The purpose of this study was to evaluate an aid in the teaching of preclinical endodontics. A control group, one-half of the students in a preclinical course in endodontics, followed the traditional program in endodontics which provided technical training by means of extracted human teeth mounted in plastic models of a dental arch. The experimental group, the other one-half of the class, first trained in basic endodontic techniques using the transparent epoxy resin blocks containing simulated root canals. Then preclinical work on extracted human teeth followed as in the control group. The two groups of students were evaluated on their performance of the biomechanical preparation of an anterior and a posterior tooth. The results indicated that the models are a valuable adjunct to the teaching of preclinical endodontics.