A new way in the fabrication of metallized nano-apertures for near-field optical microscopy is proposed. The method is based on the electrolysis between a silver metallized probe and an electrolytic glass. By dry electrolytic erosion, the metal on the tip apex is removed and lead to a very small metal free aperture. This method applied here to tapered fibers, can be extended to any other metallized tip in a rather reproducible way. ©1997 American Institute of Physics.