Loss of heterozygosity (LOH) of chromosome 22q has been investigated in 160 gliomas. LOH at one or more microsatellite increased with increasing grade of the tumor (P < 0.01). LOH22q was more frequent in astrocytic tumors (37%) compared to mixed or oligodendroglial tumors (21%) (P = 0.02). LOH22q was correlated to 10q loss but not to 1p or 9p loss. Taken together, these data suggest that LOH22q is an alteration associated with malignant progression of gliomas.