Well-differentiated liposarcomas (WDLPS) are frequently characterized by a near-diploid karyotype with supernumerary ring and/or giant rod-shaped marker chromosomes. We have shown, using fluorescence in situ hybridization (FISH) and molecular strategies, that these markers contain chromosome 12-derived sequences. Here we report the analysis of six WDLPS for the presence of amplified DNA segments by means of the recently developed comparative genomic hybridization (CGH) strategy. Two distinct chromosome 12-derived amplification units could be identified in all tumors examined, one located in the q14-q15 region as expected, the second unexpectedly mapping to q21.3-q22. Our results indicate that the concerted amplification of these two distinct regions on the long arm of chromosome 12 may be a consistent characteristic of WDLPS. These amplifications are most likely directly related to the presence of supernumerary ring and/or giant marker chromosomes in this group of soft tissue tumors.