Abstract: The ultrastructural localization of the 145/102 kDa antigens recognized by the possible protective monoclonal antibody (MeAb) M26-32 in erythrocytic stages of Plasmodium falci-parum, FCC1/HN, in vitro, was investigated by immuno-electron microscopy with LR White resin embedding and colloidal gold probe cytochemistry techniques. The results showed that the gold particles were mainly localized within the cytoplasm of ring forms, trophozoites,schizonts and merozoites of the Plasmodium. Some gold particles were found to locate on the pellicular complex of the plasmodium surface or in the cytoplasm of the infected erythrocytes. The results indicated that 145/102 kDa antigens were the common cytoplasmic antigens of asexual blood stages of Plasmodium falciparum, FCC1/HN, while a portion of the antigens could be transported to the cytoplasm of the infected erythrocytes via the pellicular complex of the plasmodium surface (Figs. 1-4).