A method of processing interferometric data relating to a sample having multiple reflective surfaces, includes the steps of: specifying a set of acceptance ranges for peaks of interest in the interferogram, based on a knowledge of the sample; determining which peaks in the interferogram fall within the acceptance ranges; identifying which peaks within the acceptance ranges represent multiple reflections and eliminating these peaks from the interferometric data; identifying acceptance ranges which do not contain peaks; and employing other peaks in the interferogram to calculate the locations of peaks in the acceptance ranges that do not contain peaks.