Studies about control processes arise from the evidence that human performance is the result of two qualitatively different processes, referred to as automatic and control processes. Subsequently, the idea of the existence of a separable system responsible for the operations related to control processes becomes more and more accepted. In accordance with Baddeley (1986) this system is called the Executive System. Models about control processes are reviewed. Particular emphasis is given to the fact that each of these models accounts only for limited aspects of the topic. It is proposed that, in order to understand the multiple aspects of voluntary control, one needs a more complete theory that explains all the aspects of cognitive system as a whole. As an example of such a theory, the cognitive theory of consciousness of Baars (1988) is presented and discussed.