The presence of localized modes in repetitive structures (i.e., systems composed of identical substructural elements) often gives rise to motions during which vibrational energy becomes spatially confined to a subset of elements. Such modes have been shown to be generated through eignevalue veering in weakly mistuned linear systems and mode bifurca-tions in perfectly tuned nonlinear systems. Recent work by the author has investigated the combined influences of weak nonlinearities and weak structural mistunings in generating localized modes. In the present work, the forced response of nonlinear cyclic systems with structural mistunings is investigated via the method of multiple scales. Under harmonic excitations, strongly and weakly localized motions will be shown to exist for various structural parameters. Sample calculations will be presented for systems composed of two, three, and four degrees of freedom. Additionally, motion confinement characteristics of such systems will be demonstrated for transient loading conditions, and the implications for novel vibration isolation designs will be discussed.