THIS method is regarded as the most promising yet adumbrated in that it reduces the problem of the synthesis of cholesterol or its stereoisomerides and analogous substances to the much simpler one of preparing a monocyclic and a bicyclic intermediate. It seems to be especially important that the double bond of cholesterol is placed by this synthetic process in the correct position and that unlike many other diene syntheses the method can be used to introduce the angle-methyl groups.