Gliomas are the most common tumors of the central nervous system and have a grave prognosis. Deletion of chromosome 10p15 is one of the most common chromosomal alterations in gliomas. Recently, a candidate tumor suppressor gene, KLF6, which is mapped to chromosome 10p, was found to be frequently mutated in prostate cancer. KLF6 is a zinc finger transcription factor and transactivates p21/WAF1/CIP expression. To elucidate the role of genetic alterations of KLF6 in gliomas, we analyzed the 4 exons of the gene by direct DNA sequencing in 155 gliomas. Of these, mutations of KLF6 were found in 9 of 76 (11.8%) glioblastomas multiforme, 2 of 28 (7.1%) anaplastic astrocytomas, 2 of 36 (5.5%) low‐grade diffuse astrocytomas and in none of the 15 oligodendrogliomas. All 13 mutations were located in the transactivation domain and most of them affected either serine residues or codons next to serine residues. Of the 13 cases with KLF6 mutation, loss of heterozygosity (LOH) at the KLF6 locus was inferred from the LOH displayed by the flanking microsatellite markers in 11 cases. We conclude that mutations of the KLF6 gene play a role in the pathogenesis of astrocytic gliomas. © 2003 Wiley‐Liss, Inc.