Summary In order to describe the surface functional behaviour, it is necessary to characterize the surface in terms of the relevant parameters involved in the mechanics of deformation. This paper, therefore, is concerned with the determination of required parameters for two randomly rough ground surfaces in contact. Applying the random process theory, the exponential density distribution of intercept length was determined analytically. The results agree with those obtained experimentally using the Optical Grating Topography (OGT) technique. This leads to the determination of the density of individual bearing areas (IBA) for different loads in terms of the parameters obtained from OGT. It is shown that the initial portion of the Autocovariance function for the CI machined ground surface is of Gaussian form. Using this result along with the density of IBA, the passible determination of cut-off relevant to contact theory is discussed.