NOWLEDGE OF THE TONGUE has always been a requirement for those dentists who would provide complete denture treatment. The tongue plays an important role during the preparation of complete dentures and an equally important part in the function of the completed prosthesis. It is well known that a large tongue increases the difficulty of making impressions but: provides greater chance of an effective border seal. Conversely, a small tongue hinders less the impression making but results in a poor border seal. It is also known that tongue-thrusting habits tend to displace mandibular and sometimes maxillary dentures. Furthermore, those patients who habitually carry their tongue in a retruded position will, more than likely, have difficulty in using the mandibular denture. Landyl and Jamieson 2 have both pointed out that the tongue carried forward will tend to aid greatly the successful utilization of a lower denture, In a natural dentition, the size of the tongue has been said to influence the size of the dental arches. Swinehart noted that a diminutive mandibular arch is found in instances of congenital aglossia. Lane* published observations on syphilitic patients who had gummatous tongues. As the tongues slowly grew larger, there was an accompanying deformity of the occlusion. Contrary to this view, Pitts5 states that he has observed narrow, crowded dental arches in Mongolian idiots who usually have large tongues. It was his contention that tongue size was not as important as tongue force in the conformation of dental arches. Obviously, the tongue size cannot be discounted as a factor in complete denture treatment because the probability is great that muscular strength is proportional to size. Balogh and LelkeG studied 130 patients over 60 years of age. The results indicated that, in contrast with other tissues, the tongue of aged persons showed no atrophic tendency. They suggested that the tendency of the tongue to hypertrophy is a common phenomenon whose occurrence is determined by the nmnber of teeth missing and by the presence or absence of dentures.