An advantage of a high-order FAS is that there exists a controller such that a linear time-invariant (LTI) closed-loop system with an arbitrarily assignable eigenstructure can be obtained. In Chapter 6, a generalized form of the conventional first-order strict feedback systems (SFSs) is firstly proposed, and a recursive solution is proposed to convert equivalently the generalized SFS into a FAS model. Then the second- and high-order SFSs are defined and their equivalent FAS models are also derived. It is further shown that, under certain common conditions, the recursive solutions for converting the generalized SFSs into FAS models can be rearranged into direct analytical explicit solutions. Such a high-order system approach is more direct and simpler than the first-order system approach since it avoids the process of converting firstly these second- and high-order SFSs into first-order ones for control. Furthermore, it can finally produce an LTI closed-loop system. Particularly, it is more effective than the well-known method of backstepping since, for the generalized complicated SFSs with more subsystems, the method of backstepping may simply be not applicable due to more serious “differential explosion” problems. Three examples are worked out to demonstrate the effect of the approach.