Objectives: The present study was undertaken to compare the pattern of expression of EGFR, cyclin D1, Ki-67, p-53 and carcinoembryonic antigen (CEA) in the epithelial lining of odontogenic keratocysts, dentigerous cysts, radicular cysts and ameloblastomas. Methods: four micrometers, formalin-fixed, paraffin-embedded tissue sections from 11 odontogenic keratocysts, 10 dentigerous cysts, 10 radicular cysts and 10 ameloblastomas were immunohistochemically studied. Results: There were statistically significant differences between cyclin D1 expression in odontogenic keratocysts and radicular cysts (p= 0.001) and ameloblastomas (p= 0.04). The differences in CEA expression between the four studied lesions were statistically significant (p< 0.0005). Proliferating cells were significantly more prevalent in odontogenic keratocysts (p< 0.0005) with a mean percentage of Ki-67 positively stained nuclei of 40%. In dentigerous cysts this mean was of 17%, of 15.5% in RC and of 7.8 in ameloblastomas. Conclusion: Some of these findings could support the theory that odontogenic keratocysts are neoplastic in origin, but other results clearly support that these lesions are developmental cysts with some neoplastic properties because of the high intrinsic growth potential.