We investigated for aneuploidy of chromosomes 7, 9, 10, 17, and p53 gene deletions in 36 glial tumor tissues, using interphase fluorescence in situ hybridization (FISH), and compared the frequencies of abnormalities between low and high grade tumors. Among the 13 low grade tumors; 1 had trisomy 7, 1 had monosomy 9, 2 had monosomy 10, 1 had monosomy 17, 1 had p53 deletion, and among the 23 high grade tumors; 10 had trisomy 7, 1 had monosomy 9, 7 had monosomy 10, 2 had monosomy 17, 6 had p53 deletion. The results indicated that neither aneuploidy of chromosome 9, nor chromosome 17 are prominent findings between low or high grade of glial tumors, although high-grade glial tumors have higher rates of trisomy 7 (43.5%), monosomy 10 (30.4%) and p53 (26%) deletion than low-grade ones. Statistical results showed significant difference between trisomy 7 and high grade astrocytomas (p = 0.031). Considering these chromosomal abnormalities we suggest that trisomy 7, loss of chromosome 10 and alterations of the p53 gene have important role associated with glial tumor development and trisomy 7 is the most important genetic changes associated with glial tumor progression.