This article concerns the identification of a class of large scale systems called "circulant systems". Circulant systems have a special property that allows them to be decomposed into simpler subsystems through a state transformation. This property has been used in literature for control design, and here we show how it can be used for system identification. The approach that is proposed here will both reduce the complexity of the problem as well as provide models which have a circulant structure that can be exploited for control design. A novel identification algorithm for circulant systems based on subspace identification is presented. The algorithm is then tested in simulation on an academic example of circulant system and on a realistic finite element model of a vibrating plate. (C) 2008 Elsevier Ltd. All rights reserved.