A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of 6beta-hydroxycortisol (6beta-OHF, 6beta,11beta,17alpha,21-tetrahydroxypregn-4-ene- 3,20-dione), 6alpha-hydroxycortisol (6alpha-OHF, 6alpha,11beta,17alpha,21-tetrahydroxypregn-4-ene -3,20-dione) and 6beta-hydroxycortisone (6beta-OHE, 6beta,17alpha,21-trihydroxypregn-4-ene-3,11,20-trione) in human urine is described. Deuterium-labelled compounds, 6beta-[1,1,19,19,19-2H5]OHF (6beta-OHF-d5), 6alpha-[1,1,19,19,19-2H5]OHF (6alpha-OHF-d5) and 6beta-[1,1,19,19,19-2H5]OHE (6beta-OHE-d5) were used as internal standards. Quantitation was carried out by selected-ion monitoring of the characteristic fragment ions ([M-31]+) of the methoxime-trimethylsilyl (MO-TMS) derivatives of 6beta-OHF, 6alpha-OHF and 6beta-OHE. The sensitivity, specificity, precision and accuracy of the method were demonstrated to be satisfactory for measuring 6beta-OHF, 6alpha-OHF and 6beta-OHE in human urine.