Cytologic smears made from minute fragments of tissue removed during neurosurgical procedures are a useful alternative to frozen sections for rapid diagnosis. We describe the cytomorphologic features of a rare brain neoplasm, subependymal giant cell astrocytoma (SEGA). On cytologic grounds this neoplasm is difficult to separate from gemistocytic astrocytoma. The clinical presentations of the two neoplasms, however, are quite distinct, with SEGA an intraventricular neoplasm mostly seen in young adults with tuberous sclerosis, whereas gemistocytic astrocytoma occurs in the cerebral hemisphere of older adults.