Abstract: A method of diagnosing a parameter of a scanning electron microscope such as magnification, linearity and stability, includes loading a reference material into a microscope, setting a permissible limit of a value of the parameters, inputting a pitch of the reference material, inputting a magnification of the microscope, acquiring a set of digital images on the reference material, analyzing the digital image line after line with determination of a pitch of features of the image in each line, in mutually orthogonal directions, checking if all lines of the digital image has been analyzed, determining a mean value of the pitch of the features in each orthogonal direction, comparing the obtained value of the pitch of the image with a known value of the pitch of the reference material to determine a ratio indicative of a modification, and determining a precision of the measurements of the pitch by statistical analysis of the pitch measurements.