Experimental and theoretical studies were made on the adsorption of benzene, toluene, p-xylene, and their binary and ternary mixtures by activated carbon in an isothermal condition of 303 K. Experimental isotherms for pure components were measured by two kinds of experimental techniques: the static volumetric method and breakthrough data analysis. Breakthrough data analysis shows that both the extended Langmuir equation and the ideal adsorbed solution theory could explain mixture isotherm data with good accuracy. In addition, a mathematical model was developed to simulate the column dynamics of pure and mixed-vapor adsorption systems. To represent the mass-transfer rate inside the adsorbent particle, the linear driving-force approximation model was applied. By optimizing the pure- and the binary-component breakthrough curve data with a dynamic model, an empirical correlation was proposed to represent the overall mass-transfer rates for the BTX vapor-activated carbon system. Results with this correlation, which is a function of the partial pressures for each adsorbate and interstitial bulk fluid velocities, showed that the prediction agrees well with the experimental data of ternary breakthrough curves.