We have compared the structures of the filamentous assembly products of different recombinant NF-L polypeptides as seen by the scanning force microscope (SFM) in buffer solution with those obtained by transmission electron microscopy (TEM) of dehydrated specimens. For SFM the filaments were immobilized on a glass surface by photocrosslinking, whereas for TEM the filaments were negatively stained and air-dried. Regarding their length and overall shapes, there is an excellent agreement between the SFM and the TEM data. However, the significant discrepancy of the filament width measured by these two microscopies illustrates the effect of the tip shape with the SFM on width measurements.