Ewing's sarcoma of bone (ESB) and peripheral neuroepithelioma (PN) are frequently considered to be different tumors. Some researchers have suggested that PN is morphologically a neuroectodermal Ewing's sarcoma. We sought to determine the extent of neuroectodermal features in conventional ESB on direct patient material (25 cases) and to compare these tumors with a similar group of readily diagnosed PNs (10 cases)