[en] Tritiation of 7-oxo-5-cholestene-3β,26-diol diacetate afforded a mixture of [5sub(α),6sub(α)-³H2] products which were reduced with lithium aluminum hydride to provide a mixture of [5α,6α-³H2]-3β, (7α and 7β), 26-triols and 3β, 26-diol. Oxidation with Jones reagent provided 3,7-dioxo and 3-oxo-[5α,6α-³H2]-5α-cholestanoic acids which were separated. Stereospecific reduction of the 3,7-dioxo methyl ester with K-Selectride followed by alkaline hydrolysis afforded (25R)-3α,7α-dihydroxy-[5α,6α-³H2]-5α-cholestan-26-oic acid. (author)