Electric charges on the surface of Plasmodium falciparum merozoites and erythrocytes were investigated by atomic force microscopy with surface potential spectroscopy. The apical end of merozoites was positively charged, while the entire erythrocyte surface was negatively charged. Transmission electron microscopy also demonstrated that negatively charged nanogold particles attached to the apical end of merozoites, and cationized ferritin particles attached to the entire surface of the erythrocyte. This indicates that the surface charge at the apical end of the merozoite may play an important role in invasion of the erythrocyte.