The standard way to achieve offset-free tracking in MPC is to add the disturbance dynamics to the prediction model and then use an observer to estimate the real disturbance. Existing algorithms only consider piecewise constant signals, while in practice it is often desirable to have a wider choice of reference and disturbance dynamics, such as sinusoids and ramps. This work provides a generalization of the disturbance estimation approach to arbitrary unstable dynamics. Zero offset is achieved under the assumption that the disturbance and reference dynamics are appropriately included in the prediction model and feasibility of the commanded reference is given. (c) 2010 Elsevier Ltd. All rights reserved.