abstract–The purpose of the present investigation was to study the effect of reducing the pleasure derived from sucking in 23 children practicing a prolonged thumbsucking habit. For this purpose a 0.5 mm thick removable cover (“splint”) was used, duplicating exact contour of teeth and palate. As a psychologic support the children were told that the sucking habit was just a pleasant occupation and that they were allowed to suck whenever they wished. Two control groups of 12 children were established, one having no splint but the same psychologic support, and one having neither splint nor psychologic support. Control after 6 months showed a significant decrease in sucking activity in the study group compared with the two control groups. Psychologic support without application of splint induced no decrease in sucking activity. The splint was worn willingly and cessation or reduction of the habit took place without any overt nervous reac