Using the transfer approach, we give, under internal stability conditions, a necessary and sufficient condition of equivalence between open-loop precom-pensation and a closed-loop configuration that consists of dynamic output feedback and inside-loop precompensation. Our result is the generalization of Hammer's result (Hammer 1983) to the general case. This result emphases the use of skew-prime relationships. The parametrization of this problem's solutions will throw new light on multipurpose controllers.