The term 'fibromatosis' is used to denote two main pathological entities: juvenile fibromatosis and adult fibromatosis. It is also possible to distinguish between superficial fibromatosis of the aponeurosis and deep fibromatosis of the muscle-aponeurosis. Histopathological findings have indicated that fibromatosis is an invasive neoformation of fibromatous connective tissue involving adjacent structures. It does not metastasize, though recurrence rates vary. Treatment is based on either excision of the mass, or radiotherapy and chemotherapy if the condition is inoperable. We describe a case of fibromatosis of the mandible in a young girl. The growth was excised completely and she was still disease-free four years later.