Ewing's sarcoma was described in 1921 by James Ewing as a diffuse endothelioma of bone and, for some time, was believed to be an undifferentiated type of Parker's sarcoma. At present, these two entities are thought to be distinct, the macroscopic and microscopic aspects of Ewing's sarcoma being very characteristic, although the exact cell type of this tumor remains unknown. This has lead many workers to study this sarcoma in order to recognize its origin. We thought it of interest to carry out cytogenetic investigations of our cases of Ewing's sarcoma, since very few chromosomal data on this malignancy exist in the literature [1-3].