16-Ketoestradiol-17[beta] and 16[beta]-hydroxyestrone are the major metabolites formed when 16-ketoestrone is incubated with slices of normal human liver and ovary tissue. About twice as much 16-epiestriol is produced as estriol. 16[alpha]-Hydroxyestrone and 17-epiestriol are produced in lesser amount. Two additional unidentified phenolic metabolites are also formed. These results are discussed in relation to the metabolism of estrogens in human tissues.