The clinical and histologic features of twenty cases of a type of papillary-cystic temporal bone neoplasm are reported. Ages of the patients ranged from 15 to 71 years. The tumors destroyed a large portion of the posterior temporal bone and included a prominent extension into the posterior cranial fossa. Patient histories indicated a slow growth rate of the lesions. Awareness of the parameters of this neoplasm, including the site of origin and probably histogenesis, may enable earlier diagnosis and more successful treatment of the tumor in the future.