The traditional version of the volume-filling micropore theory (VFMT) uses the assumption of Gaussian (or quasi-Gaussian) distribution of micropores in energy (or size). This assumption is not concluded from fundamental physical considerations. It has been shown that for most active carbons the Gibbs’ energy distribution of micropores takes place. The general form of isotherm curve for the adsorption of simple gases has been derived. The calculations with comparison with the known experimental data have been made. The results of the calculations differ much from those of the traditional version of VFMT. A new theoretical isotherm for the adsorption of vapors on active carbons has been proposed, based on the consideration of the Gibbs’ energy distribution of micropores. The theoretical isotherm has been applied to some known experimental data. The square relative dispersion is low or moderate.