Data was collected from a longitudinal study of tongue thrust beginning in 1967 by Hanson and associates. Data was gathered over a period of 12 3/4 years, starting with a group of 225 children with a mean age of 4 years, 9 months. Of this group, 61 were located and examined at or near age 18. The findings from this final evaluation were analyzed. Following the results of this study, these authors concluded that they were reasonably certain that orthodontic treatment does not eliminate tongue thrust with any appreciable degree of consistency. This study reported findings that demonstrate the unpredictability of tongue thrusting. Patients using the tongue in a normal manner before adolescence, or before orthodontic treatment, may develop a thrusting pattern at some time during treatment, or during adolescence. This study presents convincing evidence that the incidence of tongue thrust does not decline through adolescence, but rather increases slightly.