The design of electrodes' and insulators' shapes with respect to electric field stresses in High Voltage Devices is formulated as a nonlinear optimization problem under constraints. We apply a sensitivity equation method in order to achieve gradient information for the optimal design problem. This enables us to use the SQP-Algorithm for the optimization task while a FEM software package accomplishes the electric field computation. Results are presented for gas-insulated transmission lines and circuit-breakers in highly integrated switch-gears.