An interactive personal-computer program for optimizing the frequency response of linear lumped circuits (CiOpt) is presented. CiOpt has proved to be an efficient tool in improving designs where the inclusion of more accurate device models distorts the desired frequency response, as well as in device modeling. The outputs of CiOpt are the element values which best match the obtained and the desired frequency response. The optimization algorithms used (the Fletcher-Powell and Newton's methods, which, respectively, make use of approximate and exact second-order sensitivities) are fully described in DFD form. Analysis is carried out by obtaining the symbolic form of the transfer function H(s). An application example is presented.< >