At the basis of the theory of vapor adsorption in the micropores of carbon adsorbents of the most probable slit-like, limited-size type lie the dispersion interactions between the adsorbate and adsorbent atoms as well as between the atoms of the adsorbed substance themselves. As a consequence of commensurability of the pore sizes (half-widths) with those of the adsorbed molecules there occurs the volume filling of the available micropore space, i.e., the field of adsorption forces. Early stages of activation of carbons produce practically homogeneous micropores. the size of which may suitably be estimated by small-angle x-ray and calorimetry techniques involving measurements of the heats of immersion of adsorbents into liquids with different molecular size. The two methods give results that are in agreement. Dubinin and Radushkevich proposed an equation for homogeneous micropore structures with two parameters, the micropore volume W, and the characteristic energy of adsorption E,,.With deviations not considerably in excess of lo%, the product of micropore half-width x0 by E,, is a constant. For nonhomogeneous micropores the reasonable approximation is to assume the normal micropore volume distribution. The Dubinin-Stoeckli equation obtained for this general situation involves three parameters W,, EO, and dispersion 6 characterizing the distribution range. The parameters are effective since active carbons also contain larger mesopores. which exhibit weaker adsorption than micropores. The effective values of Wg, E,,. and 6, determined from the experimental adsorption isotherm of the standard benzene vapor at 293 K, allow the adsorption isotherms of other vapors within a temperature range of about 100 degrees to be estimated with reasonable accuracy. The real parameters for adsorption isotherms corrected for the adsorption in mesopores, i.e., the isotherms with the real parameters Wg, E,, and 6, can be used for calculating the geometric surface area of micropores and their volume within a given size range. Thus, the effective micropore characteristics Wi, E,,, and 6 are, together with the specific surface area of mesopores S,, , a quantitiative characteristic of the adsorption properties and microporous structure of each active carbon specimen. Benzene at 293 K and nitrogen at 77K are compared as reference vapors and their specificity is discussed.