In the present study the parental cells and glycosylation mutants of Chinese hamster ovary (CHO) cells were used to analyze the influence of surface carbohydrates on the cytoadhesion of trichomonads. Trichomonas vaginalis and Tritrichomonas foetus were allowed to interact with host cells for 2 h at 37 degrees C. Alternatively, CHO cells were treated with 10 mM periodate prior to the assays. Both trichomonads adhered to all CHO cell clones tested. A remarkable difference could be observed between the cytoadhesion of T. vaginalis and T. foetus. Sialic acid residues present on the surface of CHO cells may favor the cytoadhesion of T. foetus while hampering that of T. vaginalis. The specificity of the parasite cytoadhesion was further investigated. Sialic acid, mannose, and galactose as well as mannose, galactose, and N-acetylglucosamine added to the interaction medium at 50, 100, and 200 mM were capable of significantly inhibiting the cytoadhesion of each trichomonad species. Periodate treatment of target cells also induced decreases in the cytoadhesion of the trichomonads. These results strongly suggest an important role for host-cell surface glycoconjugates during the cytoadhesion of trichomonads. In addition, they also point out the presence of "lectin-like" molecules on the surface of both T. vaginalis and T. foetus.