SUMMARY: The gas-liquid chromatography (GLC) of some C19 steroid formates has been investigated in an attempt to speed up the final stages of the estimation of the 11-oxygenation index. SE-30 was found to give the best separation of the urinary C19 steroids formed after borohydride reduction and periodate oxidation of urine. Formates, acetates, propionates, n-butyrates, valerates and trimethylsilyl ethers were examined; formate esters gave the best separation of androsterone and aetiocholanolone. Estimation of the 11-oxygenation index by GLC increases the specificity and speed of single estimations and it is suggested that this method may find use as a rapid screening test for abnormal urinary steroid patterns.