Incubation of 3 alpha, 7 alpha-dihydroxy-5 beta-cholestan-26-oic acid and its Delta(24)-analog with rat liver homogenate produced a mixture of C-24,25 diastereoisomers of 3<alpha),7 alpha,24-trihydroxy-5 beta-cholestan-26-oic acid, a key intermediate of chenodeoxycholic acid biosynthesis.