A retrospective series of 31 purely epithelial odontogenic tumours consisted of 21 ameloblastomas, 2 adenomatoid odontogenic tumours, 2 calcifying epithelial odontogenic tumours, and 6 calcifying odontogenic cysts. Modern histological classification gives an accurate picture of some of the structural and biological differences between the above types of tumour. In spite of the, their common basis does result in some of the common features so that the precise classification of the specific tumour may pose problems or give rise to terminological disputes. For practical work it will do in the group of epithelial odontogenic tumours to insist strictly on the basic condition of the absence of either proliferating mesenchyma or hard dental tissues. This requirement naturally leads to the placing of ameloblastic odontoma outside the field of purely epithelial odontongenic tumours. Judging the biological nature of epithelial odontogenic tumours according to their structure is not reliable, a fact brought out by comparisons of ameloblastoma and adenomatoid odontogenic tumours. Rather one could rely on the nature of tumour growth. An evidently carcindependent classification pattern. Suspicion of a higher degree of malignity can be expressed by description.