An enzymatic determination of urinary 7α-hydroxy bile acids is described. The principle of the method is as follows: after hydrolysis with β-glucuronidase and solvolysis, the ethyl acetate extract is washed with alkalin solution and water, then the alkali and water washes of the ethyl acetate extract are combined and the solution is acidified to pH 1 and sodium chloride added. Shake solution with ethyl acetate to re-extract the acidic fraction and the ethyl acetate layer is evaporated. Add enzyme color solution of 7α-hydroxysteroid dehydrogenase (7α-HSD, from E. coli) to a tube of extract residue and then after incubation, measure the absorbance of the solution.