Fitting XPS peaks is done to identify different elemental components or atomic sublevels in cases where there is a complex peak shape. Also, fitting is performed to determine parameters such as peak position, height, and FWHM even for a simple, one component line. Usually Gaussian or Lorentzian line shapes (or a combination of these functions) are used for fitting purposes. Often from these determinations relative atomic amounts of the detected species are computed for the sample being studied. There are many factors that contribute to an observed peak, and a blind acceptance using curve fitting potentially can lead to erroneous interpretations of the experimental data. These mistakes can include physically unrealistic situations and the number and types of components present. In this presentation methods to better use curve fitting will be presented to minimize many of the possible problems. These practical approaches include considering the chemistry and physics of the system being studied, employing reasonable fitting criteria where appropriate, e.g., peak widths and energy separations, relative atomic area ratios, number of variables, curve types, other elements present, and the experimental conditions under which the data were obtained.