4-Hydroxyestrone 3- and 4-monoglucuronides were synthesized from catechol estrogens by means of the Koenigs-Knorr reaction with methyl α-acetobromoglucuronate. The position of the glucuronyl residue introduced was unequivocally elucidated by leading the products to the known 4-hydroxyestrone monomethyl ethers. Sulfation of 4-hydroxy-estrone with sulfur trioxide-pyridine complex followed by fractional crystallization provided 4-hydroxyestrone 3-sulfate. The isomeric 4-sulfate was prepared from 4-hydroxyestrone 3-benzyl ether by sulfation and subsequent hydrogenolysis. 4-Hydroxyestradiol monoglucuronides and monosulfates were also obtained from the corresponding 17-ketones by borohydride reduction. The preparation of guaiacol estrogen monoglucuronides and monosulfates is also described.