G-banded chromosomal analysis was performed on primary cultures of 22 intracranial tumors, including eight astrocytomas, nine meningiomas, two dermoid cysts, one acoustic neuroma, one pineal teratoma and one eosinophilic granuloma. One or more chromosomally abnormal clones were observed in 6 (75%) gliomas and 5 (56%) meningiomas. There was no chromosomal abnormality found in one of the dermoid cysts, the acoustic neuroma or the eosinophilic granuloma. A teratoma and a grade IV glioma had heterogeneous hyperdiploid karyotypes. Furthermore, astrocytomas displayed nonrandom loss of chromosomes #19, #21, #22 and Y. In meningiomas, characteristic changes involving chromosome 22 were found in 5 tumors. One meningioma had a ring chromosome in addition to chromosomal loss. With our culture and harvesting techniques, cytogenetic studies can be successfully performed on nearly all intracranial tumor explants, including those derived from small biopsy specimens. Also, in our study, specific nonrandom chromosomal anomalies were found.