SUMMARY Human fetal cells grown in tissue culture monolayers were tested using the technique of mixed agglutination and were found to possess some of the antigens controlled by the HL-A locus. Gestational specimens ranging from 6 weeks through maturity were studied. All fetal homogenates, as well as cells derived from numerous individual fetal organs, demonstrated similar patterns of reaction by mixed agglutination when tested with a panel of 22 human isoantisera. We have been unable to detect HL-A antigens on whole trophoblastic syncytia by direct mixed agglutination testing and have not demonstrated that this material is capable of absorbing out antibodies directed against HL-A specificities. Absorption studies utilizing human spermatozoa also indicate that spermatozoa, like the trophoblastic syncytia, either do not express their transplantation antigens or are lacking in these specificities.