Odontogenic cysts are classified into inflammatory and developmental origins. The most common representative inflammatory cyst is periapical cyst and the most common representative developmental cyst is dentigerous cyst and cyst which show character of tumor is odontogenic keratocyst and cyst of which cystic epithleial lining cells transform to ameloblastoma is unicystic ameloblastoma. About ten years ago p63 protein that are closely related to p53 protein was found. Authors studied about comparative pattern of expression of p63 protein in periapical cyst, dentigerous cysts, odontogenic kertocysts and unicystic ameloblastomas. Authors selected 10 cases for every four types of cyst and performed immunohistochemical staining by using monoclonal antibody about p63 protein, LSAB(labelled streptoavidin biotin) reactant and HRP(horse raish peroxidase) system. Positive cells about p63 protein were expressed at basal layer of cystic lining epithelium in periapical cysts, odontogenic keratocysts and unicytic ameloblastomas. On the contrary, in dentigerous cysts positive cells were expressed at surfce layer. Perapical cysts and odontogenic keratocysts showed significantly high values of labelling indices.(periapical cyst:72.49%, odontogenic keratocyst:64.72%, dentigerous cyst:8.94%, unicystic ameloblastoma: 5.25%) Odontogenic keratocyst showed the most strong staining intensity and the second was periapical cyst, the third was dentigerous cyst, and lastly unicystic ameloblastoma. Conclusively cause that the positive cells appeared at surface layer in dentigerous cyst reflected the position of epithelium to the enamel, and labelling indices of p63 protein were closely related to proliferative capacity and intensity of expression closely related to the labelling index and thus labelling index was also closely related to proliferative capacity of cystic lining epithelium.