Ulceration of mouth mucosa is frequently occurs after injuries in oral cavity. Oral ulcers are relatively common and these lesions cause strong pain and discomfort. Frequently, injury of the oral tissues results in abnormal fibroblast activation and keloid formation. This pathological scar formation is often associates with pain and malfunction of the organ. To understand these phenomena and develop effective treatment, reproducible animal models have to be introduced. Athymic nude mice where used to create animal models. 1% HCl acid solution was used for chemical damage of the mucosa tissue. Surgical operation was performed to create traumatic injury in the mouse oral cavity. Tissues were analyzed using immunohistochemistry methods. All of the HCl treated animals developed ulcers on the skin and mucosa of the oral cavity. Most of the mice on the place of surgical wound developed keloid tissue. Mice in which we induced pathological processes of the oral tissue, did not gain body weight. Moreover their mass had tendency to decrease. Hematoxilyn-eosin staining of the ulcerated mice tissues revealed extended coagulation necrosis - covering all tissue layers of the oral cavity. Strong local inflammatory cell infiltration and absence of proliferative cells has been demonstrated in these ulcerated and adjusted oral tissues. Morphological analysis of scar tissue revealed fibrotic hypertrophy of the injured oral tissues in these animals with the expressed infiltration of inflammatory cells. Our animal models reflect morphology of the specific injury and functionally imitate the disease.