The location of the Plasmodium falciparum vaccine candidate antigen Pf155/RESA in the membrane of infected erythrocytes was analzyed by means of selective surface radioiodination and immunofluorescence of surface-modified cells. The lack of radiolabel in Pf155/RESA as well as its localization by immunofluorescence similar to that of the N-terminal region of erythrocyte band 3 suggests that the antigen is associated with the cytoplasmic phase of the erythrocyte membrane. In concordance with this, Pf155/RESA was detected by immunofluorescence on the surface of inside out membrane vesicles from P. falciparum-infected erythrocytes. Pf155/RESA from spent culture medium also bound to inside out membrane vesicles of normal erythrocytes as well as to cytoskeletal shells of such vesicles, but failed to bind to sealed right-side out membrane vesicles. Depletion of spectrin from the vesicles abolished antigen binding, suggesting that Pf155/RESA association with the erythrocyte cytoskeleton is mediated by spectrin.