This paper deals with automated carousel systems which have been widely used in various industrial applications. We attempt to measure analytically the effects of double shuttle of the storage/retrieval machine on the throughput of standard and double carousel systems. For the double carousel system, a retrieval sequencing rule is proposed which utilizes the characteristics of two independently rotating sub-carousels. And then the expected four command cycle time models are developed under the proposed rule. Through sensitivity studies, we compare the performance of the two carousel systems working on the four command cycles with those on the dual command cycles. (C) 1999 Elsevier Science Ltd. All rights reserved.