In the last years, the manipulators with parallel topology have begun to be more and more used because of their unexploited potential. The usage of the manipulators with parallel topology instead of the manipulators with serial topology presents a series of advantages. A disadvantage of the usage of the manipulators with parallel topology would be the dimension of the workspace which is limited. Within this paper, the authors optimize the geometric parameters of the five-bar manipulator according to the given workspace by using the method of the genetic algorithms. The method helps the designer to dimension the geometrical parameters according to the workspace which is demanded.