We report on the use of the extended logistic function for fitting Auger-electron (AE) and secondary-electron (SE) line scans. Such fits provide convenient and objective measures of parameters describing the interface width and possible asymmetry of a line scan. We show examples of fits to AE and SE line scans for three types of samples. Fits to AE and SE data for a gold island on a carbon substrate gave useful measures of the lateral resolution of a scanning Auger microscope and "tails" present in the line scans showed evidence of imperfect alignment of the microscope. Fits to AE spectra obtained as the primary beam was scanned across an edge of Cr/Cr2O3 lines on an indium tin oxide substrate showed similar tails due to the effect of backscattered electrons on the generation of Auger electrons for primary energies between 15 and 25 keV. Fits with the logistic function to SE line scans across a fractured Ni/Cr multilayer sample and to AE and SE line scans across a sputtered crater of this sample provided useful measures of the interface width. (c) 2006 American Vacuum Society.