The murine monoclonal antibody H316 recognizes cell surface glycoproteins shared in expression by human trophoblast and peripheral blood leukocytes. It is also strongly expressed by many human tumor cell types, including choriocarcinoma and teratocarcinoma. The H316 antigenic determinant from these different cell types is carried on two wheat germ agglutinin-reactive glycoproteins of approximately 65,000 and 55,000 m.w. The antigenicity is not dependent on N-linked glycosylation. Biochemical fractionation procedures suggest that the molecules are related to each other, are not associated through intermolecular disulfide bonds, but do exhibit intramolecular disulfide interactions. These glycoproteins demonstrate m.w. heterogeneity between different cell lines and individual trophoblast membrane preparations. Such properties suggest that H316 molecules may be representative of TLX antigens (trophoblast-leukocyte common antigens), which have been suggested to influence maternofetal immunogenetic interactions.