We analyzed 72 primary and 25 recurrent glioblastoma multiforme (GBM) samples for DNA sequence copy number abnormalities (CNAs) by comparative genomic hybridization (CGH). The number of aberrations per tumor ranged from 2 to 23 in primary GBM and 5 to 25 in recurrent GBM. There were 26 chromosome regions with CNAs in more than 20% of tumors. 7q22-36 was the most common gain and 10q25-26 was the most common loss; each occurred in more than 70% of tumors. Of 27 amplification sites, epidermal growth factor receptor (EGFR) was the most common; it was observed in 25% of primary GBMs. Statistical analysis based on pairwise correlation of CNAs indicated that there is more than one class of primary GBM.