Coprime factorization originates from algebra studied by French mathematician E. Bezout . In recent years, it has been used to describe dynamic systems . Coprime factorization can be applied in controller synthesis for a given dynamic system with uncertainties [7, 8]. The factorizations can be further employed to construct the set of all stabilizing controllers for the system and to represent a simple parameterization of all stabilized closed-loop transfer functions. In addition, the normalized coprime factorization which will be introduced in this chapter has a strong link to the H∞ loop-shaping problem . It is also relevant to the spectral factorizations and internal stability.