The robustness properties of sliding-mode and H-infinity controllers are exploited to produce a dynamic output feedback controller that is insensitive to matched perturbations and attenuates the unmatched ones. The assumptions on the plant differ from the standard assumptions of the Riccati state-space approach to H-infinity control. The sliding-mode controller drives the state into a reduced-order manifold for which the equivalent system does satisfy the standard assumptions and hence the standard theory can be applied. The resulting Riccati equations are of reduced order. (C) 2011 Elsevier Ltd. All rights reserved.