Deletions of loci on chromosome 11p have been found frequently in several malignant tumors including gliomas, suggesting the presence of tumor suppressor genes. We analyzed 38 gliomas [26 malignant gliomas (grades III and IV) and 12 less malignant gliomas (grade I and II)] for loss of heterozygosity using microsatellite sequences on 11p as polymorphic markers. Loss of heterozygosity was found in 8 of 26 malignant gliomas (31%) but not in the less malignant gliomas. In the region with loss of heterozygosity, loci on 11p15.5-pter were commonly deleted. Our results suggest that a putative tumor suppressor gene involved in malignant progression of gliomas is located in an approximately 21-cM region on 11p15.5-pter.