Soft tissue sarcoma fresh specimens from 23 patients were screened for genetic abnormalities of 3 cellular oncogenes, i.e., c-myc and c-myb and c-Ha-ras. Southern blot hybridization analysis demonstrated amplification of the c-myc gene(4- to 8-fold) in 7 cases, i.e., 3 malignant fibrous histiocytomas, 1 liposar-coma, 1 fibrosarcoma, 1 lymphoma of the soft tissues and 1 synovial sarcoma. Amplification of the c-myc genewas not associated to other genetic alterations such as gene rearrangement. Hybridizations with c-myb and c-Ha-ras probes showed no gene abnormalities in this series. Our results indicate that c-myc oncogene amplification may play an important role in the development of certain soft tissue sarcomas as it has been found for other human malignancies. The clinical significance of these features remains to be established.