SUMMARY The specificity of the method of Stern [1957] for the determination of urinary pregnanetriol has been examined using chromatography on alumina columns and paper. The pregnanetriol fractions were found to contain chromogenic impurities, most of which could be removed by the addition of a pre-wash of 3% ethanol/benzene to the system described by Stern for the elution of pregnanetriol from alumina. The reliability of the modified method has been assessed with special reference to specificity.