This monograph reports the development of an approach to computer-aided control system design (CACSD). Of primary concern is the quality of cooperation between the designer and his computer. The designer is suggested to treat a CACSD problem as a search problem, in which he and the computer cooperate to locate satisfactory designs among sets of candidates. Interactive Multi-Objective Programming (IMOP) is employed to define the level of abstraction as well as the organization of the design facilities in the computer.