Erythrocytes infected with malaria parasites often contain membranous vesicles that are presumed to facilitate macromolecule traffic between the parasite and erythrocyte membranes. One such vesicle network, called Maurer's clefts, is expressed in Plasmodium falciparum-infected erythrocytes and contains a 50-kD polypeptide. Using a monoclonal antibody reactive with this polypeptide, we show that hepatic stages of P. falciparum express an epitope common to this blood-stage antigen. In addition, this epitope is cross-reactive with antigens expressed by primate leukocytes and platelets. Such epitopes may induce autoantibodies commonly seen in patients with malaria.