A simplified theory is presented for the derivation of optimum matching networks for a restricted class ofRCLloads. It is applied also to the case of matching from a specified source network to a specified load network, and to optimum networks for transference of power from an infinite-impedance source to a given load network, which are particularly useful for interstage-network design. The applications of frequency and impedance transformations are fully described. The procedures are illustrated by numerical examples.