The surface potential fluctuations can have significant effects on both the magnitude and shape of the measured small-pulse DLTS spectrum. An increase in the dispersion parameter of the surface potential distribution, which is assumed to have a Gaussian form, leads to a reduction in the DLTS signal size, a shift of the peak position and a broadening of the peak shape. A computer program including the exponential temperature dependence of hole capture cross section, , was developed to analyse temperature-scan DLTS spectra of a MOS structure; in the evaluation procedure , and are taken as fitting parameters. A bias dependence of has been found and an interpretation of this behaviour has been attempted in the light of random point charges (Brews) and patchwork (Nicollian-Goetzberger) models.