There are few descriptions of the cytologic features of subependymoma because this neoplasm is rare and most commonly encountered incidentally at autopsy. Here we report a surgical case of subependymoma occurring in the lateral ventricle and provide the first documentation of the crush cytologic features of this tumor. A 34-year-old woman was found to have a tumorous lesion in the right lateral ventricle. At surgery, a 2-cm-diameter tumor was detected in the anterior horn. Histologic examination during surgery revealed that the mass was composed of loose,fibrillary networks and clusters of nuclei showing mild pleomorphism. A number of microcystic formations were evident. Histologically, the neoplasm was considered benign--specifically, a subependymoma. Papanicolaou- or Giemsa-stained crush specimens and imprint smears were also prepared. The cytologic morphology was fundamentally the same as the histologic. In the crush specimens, microcystic formations were readily visible. Moreover, details of the cellular morphology were more easily recognized in the cytologic slides than in the frozen sections. Cytologic examination, particularly crush cytology, appears to be useful for the rapid diagnosis of subependymoma during surgery in combination with the examination of frozen histologic sections.