Twenty lipomatous tumors, including eight lipoma-like liposarcomas and 12 benign lipomas, were analyzed using comparative genomic hybridization (CGH). DNA sequence copy number changes detected in five lipoma-like liposarcomas (mean, 1.1 aberrations/tumor; range, 0-2) consisted of gains of 12q13-21 (five tumors) and 1q21-23 (four tumors). Two of the tumors showed high-level amplification at 12q14-21 and one tumor at 1q21-22. No copy number changes were found in lipomas. Overrepresentation of 1q and 12q sequences was a recurrent finding in lipoma-like liposarcomas but not in lipomas. Thus, CGH may help in the differential diagnosis of low-grade or borderline adipose neoplasms.