The occurrence of unicystic ameloblastoma has been studied in 20 patients presenting with unilocular cystic lesions whose clinical, radiographic and gross features were those on non-neoplastic cysts. In the majority of these, the lesion mimicked dentigerous cyst. The rate of recurrence for this group of lesions as determined by long term follow-up observation available for the majority of patients was distinctly lower than that associated with multicystic character of the lesion throughout its course, is indicative of a much less aggressive variety of neoplasm. The adequacy of simple enucleation as a modality of treatment in the majority of patients with this type of lesion is suggested. It was not possible to answer the question whether or not the ameloblastoma began in antecedent non-neoplastic cyst.