Two unusual cases of central odontogenic fibroma are described and used to illustrate differential diagnostic problems in this controversial group of lesions. The first case had a cystic lesion noted on routine radiography in the left ramus of the mandible. This particular case was unusual histologically as it showed in addition to typical areas of odontogenic fibroma a small inflamed cyst lined by epithelium containing many hyaline bodies. The second case presented with anaesthesia of the right lower lip and an enlarged chin prominence. The lesion was diagnosed as an odontogenic fibroma but with a somewhat unusual histological appearance in that there were abundant areas of osseous metaplasia throughout the lesion.