The goal of this review was to determine the prevalence of cysts in the oral and maxillofacial regions, specially odontogenic cysts, as determined by age, sex and location.This research reviewed 6826 biopsies from department of oral pathology school of dentistry at the medical sciences university of Tehran from 1360-1376 (1981-1997).The results obtained revealed that 19.48% of biopsy lesions were cysts of osseous structures, of which 81.9% were odontogenic cysts, 12.4% psuedocyst and 5.7% were Non- odontogenic in origin.The most common lesions of the oral cavity were odontogenic cysts of which the subgroup of radicular cysts (which belong to the category of inflammatory odontogenic cysts) consisted of 49.15% radicular cysts occurred with the higher incidence in males in their third decade of life and were found most commonly associated with the upper jaw.Dentigerous cysts fall in the second most common group at 25.71% of odontogenic cysts.These cysts had a male predilection with a peak incidence in the second decade and were most common in the lower jaw.In the third group were the keratinized odontogenic cysts at 19.25%. These cysts had a male predilection with a peak incidence in the third decade and the lower jaws were twice as likely to be involved as the upper jaw. Other types of odontogenic cysts were noted to be less common in occurrence.In this study it was discovered that mcoceles consisted of 63.5% of pseudocysts and were found most commonly in the lower lip, with surgical ciliated cysts at 33.7% were the most common Non- odontogenic cysts and were found exclusively in the upper jaw adjacent to the maxillary sinus.Over all it can be stated that about y5 of all oral and maxillofacial lesions were cysts.The most common cysts were odontogenic cysts which due to their higher prevalence and various types, most be carefully examined at the histopathological level to diagnose and therefore administer definitive treatment.