Very little is known concerning the cytogenetic and molecular genetic changes of low-grade central osteosarcoma, a rare form of osteosarcoma. In the present study, we used comparative genomic hybridization (CGH) to screen for DNA sequence copy number aberrations in 10 samples from 6 patients: 7 typical low-grade central osteosarcomas, one low-grade (Grade II) central osteosarcoma, and two high-grade (III and IV) local recurrences of a low-grade central osteosarcoma Nine samples had aberrations. Six typical low-grade central osteosarcoma samples had a single DNA sequence copy number change per tumor. Three samples from more advanced tumors (a Grade II low-grade central osteosarcoma and local recurrences of Grade III and IV) had a mean of five changes per tumor. Recurrent changes affected these minimal common regions: +12q13-q14 (three tumors), +12p (two tumors), and +6p21.1-p21.3 (two tumors). Nine samples were analyzed for CDK4 and MDM2 expression and SAS amplification. One sample with a gain of chromosome 12 had a very strong expression of MDM2, strong expression of CDK4, and amplification of SAS. One sample with a gain of 12q13-q14 had strong expression of CDK4 and MDM2. Strong expression of CDK4 was found in two additional tumors; one had a gain of 12q13-q21, and the other had no changes in chromosome 12 by CGH. No alterations were detected in the CDK4, MDM2, and SAS panel in three other samples with no changes in chromosome 12 by CGH. In conclusion, the low number of DNA sequence copy number alterations reflects the relatively low malignancy of low-grade central osteosarcoma. This simplicity differs from the complex aberrations seen in conventional high-grade osteosarcomas.