The Δ13,17a-C-nor-D-homo-spirostan olefin has been characterised. The epoxides derived from this olfin, and from the isomeric Δ17a,18-olefin have been made and their configurations determined, by the study of the tert-alcohols derived by reduction with lithium aluminium hydride. The boron trifluoride and perchloric acid catalysed reactions of these four epoxides have been studied. An attempt was made to synthesise and study the boron trifluoride catalysed rearrangements of the analogous C-nor-D-homo pregnene epoxides. The epoxides of 12-methylene tigogenin acetate have been made and their configurations determined by the study of the dehydration reactions of the tert-alcohols formed by reduction of the epoxides with lithium aluminium hydride. The Grignard reaction of the C12-ketone of hecogenin acetate was shown to proceed from the β-face. Dehydration of this alcohol gave the Δ11,12 olefin from which the 12β-methyl-11#945;,12#945;-epoxide was made. The boron trifluoride and perchloric acid catalysed rearrangements of this epoxide, along with the two 12,12'-epoxides, was studied.