We discuss the origin of adsorbed-phase nonuniformity and its implications for the prediction of a multicomponent adsorption equilibrium in microporous adsorbents. Current treatments of adsorbed phase nonuniformity are reviewed and a new model, the multispace adsorption model (MSAM), is presented. The MSAM multicomponent predictions have as inputs the pure-species adsorption isotherms and a single parameter characteristic of the adsorbent. We extend the original formulation of the model to include the temperature dependence of the parameters. Our model’s performance is compared with that of the other thermodynamic models for multicomponent adsorption using our own experimental results and the literature data.