Two cases of sellar chordomas are reported, with ultrastructural and histochemical study. The embryological origin and the histochemical data are discussed. The question of chondroid chordomas is evoked and the results of the ultrastructural study are interpreted on the basis of the cases hitherto reported. Special attention is called to the methods for the detection of polysaccharides by electron microscopy in such proliferations. Tissue culture seems to be able of providing a good information as to the secretory activity of the chordomas located at the skull base.