Oligodendroglial and ependymal tumours are not the most common glial neoplasms; however, they are important subtypes of gliomas with different tumour biologies. Cytogenetic information has suggested that losses of chromosomes 1 p and 19 q are the most frequent genetic alterations in oligodendroglial tumours. Combined loss of these chromosomes has been associated with better chemotherapeutic response and prolonged overall survival. Loss of chromosome 22 is a well defined abnormality in ependymomas. In addition, deletion of chromosome 6 q may be another frequent chromosomic aberration in paediatric ependymomas.