Objective To detect the PTEN gene mutation and loss of heterozygosity(LOH) on chromosome 10q in oligodendrogliomas. Methods The entire PTEN coding sequence of the 9 exons were screened by 9 different PCR reactions and followed by denaturing gradient gel electrophoresis(DGGE) and direct sequencing for detecte mutation.Microsatellite markers with fluorochrome on 10?q amplified by PCR were used to detecte LOH by PAGE on an automatic sequencer and analyzed with the Gene Scan program in 55 oligodendrogliomas and mixed oligodendrogliomas. Results The PTEN gene somatic mutations were detected in 2 tumors,one case that carried a PTEN mutation deletion T base in position 20 resulting stop codon moved to 347.Another case was a A to C transition at the codon 139 resulting in changeing from Leu to Phe.Twenty\|three of 55(42%) cases were observed the loss of heterozygosity(LOH) on chromosome 10?q.Fifteen of 55 cases allelic loss were detected on loci D10S 541 which located in the PTEN gene region at 10?q 23\^3 .Twelve of 55 cases were detected totaled LOH on 10?q.Conclusion\ The PTEN gene mutation is rare,loss of allelic 10?q is frequente in oligodendrogliomas,especially in high\|grade oligodendrogliomas.It could indicate that LOH on 10?q has an enhance effect in tumor progression,and chromosome 10?q harbors additional tumor suppressor genes in oligodendrogliomas.\;[