The margins usually appear distinct and well corticated in plain radiographs, but a disappearing margin sometimes is seen When the CT window is adjusted for bone, a very thin layer of subperiosteal new bone often will be found in the same areas appearing to be burnt out or perforated in plain radiographs. This may be a characteristic feature of amelo- blastic fibroma on CT scans, and its presence may explain the low recurrence rate of this tumor. In one instance we observed a very thick solid cortical reaction. In their review of the literature, Blankestijn and colleagues (1986) found that 65% were described as multilocular. Nilsen and Magnussen (1979) observed this appearance in two of their four cases, and other authors had similar findings. In such instances, Worth (1963) stated that the lesion resembles an ameloblastoma. In contrast to the ameloblastoma