Approximately 30%-35% of human glioblastomas have epidermal growth factor receptor (EGFR) gene amplification. Amplicons containing the EGFR gene frequently include several unidentified adjacent genes. Amplification of adjacent genes in the absence of EGFR amplification has been documented. To define the region in detail, we produced a YAC contig map, determining the orientation of the EGFR gene and the general order of 11 STS and EST markers. Seventy-six tumors with amplification of the region were found in a series of 246 human astrocytic gliomas. The amplicons showed amplification of contiguous or noncontiguous loci both telomeric and centromeric to the EGFR gene. Six percent (12/190) of the glioblastomas and 1 anaplastic astrocytomas had amplicons excluding the EGFR gene. These amplicons commonly contain amplified loci telomeric to the EGFR gene. Some of the amplified loci were found to be consistently overexpressed. The findings suggest that there may be other gene target(s) for amplification in the 7p12 region in addition to EGFR.