Asexual blood forms of the human malaria parasite, Plasmodium falciparum, synthesize a major glycosylated 195 kDa protein that has been considered for the development of a vaccine. beta-Elimination-borohydride reduction of the 195 kDa glycoprotein and its 16 kDa processed product after metabolic labeling of their carbohydrates, showed the presence of derived, labeled glucosaminitol and alanine. This suggests that the 195 and 16 kDa glycoproteins contain distinct O-glycosyl linkages and that N-acetylglucosamine and serine residues are involved in the attachment of carbohydrate moieties to the protein core. Endo-O-glycanase treatment of total glycoproteins shows that O-glycosidycally-linked sugars represent a major carbohydrate moiety in P. falciparum glycoproteins.