Ewing's sarcoma is the second most common bone tumor in childhood, with an overall 5-yr survival of 40%. It is one of the poorly differentiated small spherical cell tumors frequently requiring distinction from rhabdomyosarcoma, neuroblastoma, osteosarcoma, primitive neuroectodermal tumor, and lymphoma. The majority of rhabdomyosarcomas, neuroblastomas, and osteosarcomas are aneuploid, whereas Ewing's sarcomas are usually diploid. To determine whether there is any correlation between DNA content, morphology, site, and survival in Ewing's sarcoma and extraosseous Ewing's sarcoma, 21 tumor samples were studied retrospectively (3 extraosseous Ewing's and 18 Ewing's sarcomas). The DNA analysis was performed on disaggregated paraffin-embedded tissue nuclei by flow (FCM) and image (IC) cytometry and correlated with the histology and clinical history. The DNA ploidy by FCM on 17 of 18 Ewing's sarcoma samples was 12 diploid, 1 aneuploid, and 4 tetraploid. By IC, the DNA ploidy on 16 samples was 13 diploid, 1 aneuploid, and 2 tetraploid. Three samples were nonevaluable (1 by FCM and 2 by IC). The agreement between FCM and IC was 12 of 16 (75%). The extraosseous Ewing's sarcoma tumors were 2 diploid and 1 aneuploid by IC. In this study there was no correlation between the DNA ploidy and either the histology, site, or survival.