The purpose of this paper is to present a new systematic procedure for decoupling and command tracking of multivariable, nonlinear, and unstable systems. The design methodology is based on stabilization of the multivariable system followed by generating its describing function models; two algebraic procedures for decoupling and tracking are utilized. Finally, the design must be verified by a nonlinear simulation to make sure that approximations made during design are valid. This is the first paper in the area of simultaneous decoupling and signal tracking of multivariable nonlinear systems that is based on the application of the describing function technique and two other algebraic techniques.