The presence of terminal alpha-D-galactosyl residues in the carbohydrate chains of glycoprotein antigens from the asexual blood stages of Plasmodium falciparum is demonstrated by the alpha-D-galactosidase sensitivity of particular parasite antigens, the use of specific glycosidases to cleave sugars from parasite glycoproteins radiolabeled with [3H]glucosamine, and the ability of Bandeirea simplicifolia lectin, which has a specificity for terminal alpha-galactosyl residues, to bind to the parasite. The carbohydrate side chains, and in particular the terminal alpha-galactosyl residues, are shown to have an important role in determining the binding of antibodies to parasite glycoproteins.