Pulsed-force-mode atomic force microscopy (PFM-AFM) using a cantilever with aSi3N4tip was applied to map charge distribution on a sample surface in water. In order to confirm the applicability of the present PFM, we prepared a patterned sample by vapor deposition of Al on a quartz plate covered with silica beads, followed by oxidation of Al withO2and removal of the beads with ultrasonication. The two different areas ofAl2O3andSiO2had different isoelectric points and bore positive and negative charge, respectively, atpH 8.6. The lateral resolution of the present method was found to be ca. 30 nm. ©1997 American Institute of Physics.