Our aim was to investigate the effect of sclerosant agent OK-432 on tongue fibrosis and to determine whether the fibrosis formed by this substance increases with dose. Fifty Wistar albino rats were divided into three groups for the study. In the first group 0.2 ml OK-432, in the second group 0.5 ml OK-432, and in the third group physiological saline as the control substance was injected into the tongue of these rats. Subjects were sacrificed on the first day, first week, first month, third month and sixth month following the injection. Cross-sections of the tongues were stained with hematoxylin-eosin (HE) and Masson Tri-chrome. The degree of fibrosis was measured using ocular micrometry. A significant amount of fibrosis was observed in both the 0.2 ml (P = 0.020) and 0.5 ml (P = 0.003) OK-432 injection groups. OK-432 is a material that causes significant fibrosis in the muscle when compared to physiological saline. The degree of fibrosis in the tongue increases with dose.