High frequency of allelic deletions was detected at marker D10S215 (80%) at the proximal 10q23 region in both oligodendroglial and ependymal tumours and between markers D10S216 (42%) and D10S169 (67%) at distal 10q25-26 region in oligodendroglial tumours.No mutations of PTEN/MMAC1 were found. p53 mutations were detected in three oligoastrocytomas and one ependymoma; three out of five mutations were found in exon 4.