The prediction method for the adsorption equilibria of binary gaseous mixtures on a heterogeneous surface using only experimental isotherms of pure components is presented. The experimental isotherms were analysed by Ross and Olivicr's model isotherms. The heterogeneous surface of the adsorbent was considered as the ensemble of the 1000 homogeneous patches of the different adsorption energies which distribute in a Gaussian form. The equilibrium coefficient was obtained for each patch and for each component. These coefficients for component 1 were numbered consecutively from 1 to loo0 in the order of the adsorption energy, and each coefficient was combined to the coefficient of the corresponding number of component 2, one by one. The adsorption equilibrium was calculated by Hill-de Boer equation for mixtures for 1000 combinations of the equilibrium coefficient of components 1 and 2. The amount adsorbed of each component could be obtained as the average value over the loo0 combinations. The results agreed with the experimental data for the mixtures of ethylene and ethane, and ethylene and propylene on a carbon molecular sieve at 30Β°C (20, 50 and 100mmHg) and at 30Β°C (20 and 50mmHg), respectively.