To deal with the demanding goals of the restricted Diesel emission leg islation the focus in the application of exhaust after treatment systems to fu lfill these strict requirements moves more and more to model based design, optimization and contr ol. Against this background a nonlinear model predictive control (MPC ) for an exhaust after treatment system consisting of a DOC (Diesel oxidation catalyst), a DPF (Diesel particulate filter) and a SCR (selective catalytic reduction) is proposed. Similar t o standard ammonia control schemes also in this study the dosing amount is the only adju stable input variable. But in contrast to these usually simple feed forward dosing approac hes in this proposal also information about the nonlinear temperature behavior and the sto rage effects of the SCR - included in a nonlinear SCR model - can be considered for the ammonia c ontrol. Based on these improved knowledge of the system a nonlinear model predictiv e controller, also applicable for real time tests on the engine, is applied for SCR control leading t o promising results in simulation.