SUMMARY A new chromatographic procedure for determining small amounts of pregnanediol in urine is described. The method involves (1) acid hydrolysis, (2) toluene extraction, (3) a new permanganate oxidation step, (4) chromatography on alumina columns, (5) acetylation, (6) further chromatography on alumina, and (7) colorimetry after developing a colour with sulphuric acid. The method is considered under the headings of specificity, sensitivity, accuracy and convenience. The significance of results obtained from male, proliferative phase female, and post-menopausal urine is discussed.