Résumé : The geometry of glass knife edges for ultramicrotomy was studied wilh nanoscale resolution using scanning force microscopy (SFM) in the contatct mode. The local shape of the cutting edge was estimated from single line profiles of the SFM topographic images by taking into account the exact radius of the ultrasharp silicon lip. The tip radius was estimated from secondary electron micrographs recorded at low voltage by field emission scanning electron microscopy (FESEM). The radius of the investigated cutting edges was found to be in range 5-20 nm. The results obtained illustrate that the combinition of SFM and high resolution FESEM provides a unique means 10 determine precisely the radius of glass knive