In the present paper we investigate the problem of modal-control using proportional-plus-derivative output-feedback controllers (PD-type). With the derivative part of the feedback, we can get additional information about the system state vector, which are necessary for the solution of the pole-assignment problem. This group of PD-controllers has the advantage of providing additional parameters without increasing the order of the system under control. The additional derivative term of the system output-compared with purely proportional controllers-helps to reduce the overshoots in the system outputs during the transient period, thus it has no effect on the steady-state characteristics of the system, and it also improves the system stability. A sufficient condition for complete pole-assignment of closed-loop system is derived in the form of lemma. A simple and computationally easy design procedure of PD-controllers is developed, and it is applied to the synth-esis of stabilizing systems of a helicopter.