This chapter discusses the dynamics of adsorption beds. The material balance for a single-adsorbed component is presented and solved using a state variable approach. Gradual transitions and abrupt transitions are shown to depend on the adsorption isotherm. Desorption transitions are also discussed, and the number of bed volumes needed to remove an adsorbate is presented. The solutions are shown independent of mass and heat transfer effects. A brief discussion of multicomponent adsorption in fixed beds is also presented.