Abstract: Dispersivity has been recently identified as a basic physical property of oil reservoir rock, which can be taken as a measure of the ability of unstable mixing of tow miscible fluids in porous media during miscible flooding. In this paper the theory and method used for determining dispersivity experimentally are described. According to the experimental results the correlations of dispersivity with other characteristic parameters of rocks, such as permeability, average grain size, capillary pressure, Kovals heterogeneity factor etc, and those with the waterflooding efficiency are discussed.