In 1973, Heffelfinger and coworkers described a variant of chordoma that contained cartilaginous areas indistinguishable from hyaline type chondrosarcoma. They designated these tumors chondroid chordomas and found that they had a better prognosis than classic (nonchondroid) chordomas. Since that time, there has been an ongoing debate over whether chondroid chordoma is best considered a distinct clinicopathologic entity separable from chondrosarcoma or a misdiagnosed chondrosarcoma whose concept developed from the erroneous interpretation of morphology. In an attempt to clarify the issue, the authors used light microscopy and immunohistochemistry to study 12 chondroid chordomas, 38 classic chordomas, and 28 chondrosarcomas that arose in the base of the skull or spine. As a reference, they also analyzed the immunohistochemical profile of fetal notochord, ecchordosis physaliphora, and fetal hyaline cartilage. They found that all chondroid and nonchondroid chordomas were positive for cytokeratin, and the majority were also positive for epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA). In contrast, none of the chondrosarcomas stained for cytokeratin, EMA or CEA. Vimentin and S-100 were positive in more than 95% of both classic and chondroid chordomas and chondrosarcomas. The immunohistochemical profile of these tumors was similar to the pattern of immunoreactivity of their nonneoplastic counterparts. The authors conclude that chondroid chordomas is a variant of chordoma and should not be confused with chondrosarcoma. Because chondroid chordomas have been reported to have a better prognosis, they felt that this nosologic term should be preserved and that chondroid chordoma should continue to be a focus of clinical and pathologic study.