Ameloblastic carcinoma is a rare malignant lesion with characteristic histologic features and behavior that dictates more aggressive surgical approach than that of a simple ameloblastoma. However, reliable evidence of its biologic activity is currently unavailable due to the scarcity of well-documented cases. It occurs primarily in the mandible in a wide range of age groups; no sex or race predilection has been noted. It may present as a cystic lesion with benign clinical features or as a large tissue mass with ulceration, significant bone resorption and tooth mobility. Because the lesion is usually found unexpectedly after an incisional biopsy or the removal of a cyst, a guide to differential diagnosis is not usually useful. The identifying features of ameloblastic carcinoma must be known and recognized by dental practitioners. The tumour cells resemble the cells seen in ameloblastoma, but they show cytologic atypia. Moreover, they lack the characteristic arrangement seen in ameloblastoma. Direct extensions of the tumour, lymph node involvement and metastasis to various sites (frequently the lung) have been reported. We present a case of ameloblastic carcinoma of the mandible with a clinical course of typical aggressiveness and extensive local des- truction in a 27 year old male patient.