26,27-Oxido-5 a -cholestane-3 a ,7 a ,12 a -triol can be obtained in a homogeneous state in gram quantities by passing it through one PrepPak-500/Silica cartridge mounted in a Waters Assoc. preparative liquid chromatograph. The elution solvent was methanol–chloroform (1:14). The isolated material was analyzed for purity by several chromatographic means and by elemental analysis, and was finally characterized by the usual spectroscopic means. Gas–liquid chromatography of its trimethylsilyl ether indicated the formation of a tetrakis-trimethylsilyl-26-chloro derivative, in addition to the expected tris-trimethylsilylated substance. The structure of the former compound is deduced from the fragmentation and isotope abundance in its mass spectrum and from chemical principles.