The case of a 75-year-old woman with voluminous bilateral symmetrical masses of the parotid glands is reported, and the literature relevant to the differential diagnosis in bilateral neoplastic and nonneoplastic parotid masses is reviewed. The presurgical workup was based on clinical evaluations, nuclear magnetic resonance imaging findings, and cytologic examination to obtain the differential diagnosis. Benign or malignant tumors were excluded. Surgery was performed for esthetic reasons and in consideration of progressive enlargement of lesions. Histopathologic examination of resected masses revealed benign lymphoepithelial cysts with polyclonal infiltration of lymphoid cells. Serological testing for tuberculosis, cytomegalovirus, human immunodeficiency virus, and Epstein-Barr virus (EBV) and testing using the in situ hybridization technique for the presence of cytomegalovirus and EBV were negative for productive infection or viral replication. A diagnosis of retention cysts was suspected on the basis of presurgical evaluation, histopathological examination, and serologic analysis. In this case, bilateral obstruction of the parotid ducts by a mobile denture probably played the main role in the pathogenesis and development of bilateral parotid retention cysts, because any other specific cause for the pathogenesis was not found with diagnostic tools.