6 alpha-Hydroxy metabolites of cortisol were determined in the urine of pregnant (36-40 weeks of gestation) and nonpregnant women and in amniotic fluid from nearly fullterm pregnant women because relatively large amounts of these compounds are excreted in the urine of 2-day-old infants (> 200 micrograms/day). The corticosteroids analyzed by high pressure liquid chromatography and gas chromatography-mass spectrometry were 6 alpha-hydroxy derivatives of (allo)tetrahydrocortisone (3 alpha, 17 alpha, 21-trihydroxy-5 epsilon-pregnan-11,20-dione), (allo)tetrahydrocortisol (3 alpha, 11 beta, 17 alpha, 21-tetrahydroxy-5 epsilon-pregnan-20-one), and alpha- and beta-cortolone (3 alpha, 17 alpha, 20 epsilon, 21-tetrahydroxy-5 beta-pregnan-11-one). All of these compounds were found in the urine samples from both groups of women and in the amniotic fluid samples in contrast to those found in the urine samples from the neonates where 6 alpha-hydroxy compounds of (allo)tetrahydrocortisol and allotetrahydrocortisone were not positively identified because of insufficient yields. The pregnant women excreted significantly larger amounts of 6 alpha-hydroxy metabolites of cortisol (approximately 600 micrograms/day) than the control women (approximately 90 micrograms/day), and the rate of urinary excretion of these 6 alpha-hydroxy compounds was 7.82 and 1.30 micrograms/kg . day, respectively, for these groups of women compared to 54.3 micrograms/kg . day for the neonates. The precursors of these metabolites within the fetal body originated largely from the maternal circulation, and, therefore, the 6 alpha-hydroxy metabolites of cortisol excreted by the mother refer mainly to fetal metabolism and to a lesser extent, to the fetal secretion of cortisol.