The sequencing problem in carousel systems was first considered by Bartholdi and Platzman (1986). They assume that the orders are picked one at a time, which leads to two sequencing problems, i.e., the pick sequencing within an order and the sequencing of orders. The effect of the latter is not+ significant when the order arrival rate is small com- pared with the order retrieval rate, so the problem simplifies to the pick sequencing within the orders. They present a polynomial algorithm to optimally solve this problem, as well as some simple heuristics that are easier to compute and perform well when the number of picks is large relative to the total stor- age space. When the order arrival rate is large, the sequencing of orders must be considered in minimiz- ing the unproductive time of traveling from the end position of one order to the start position of the next. In this case, an efficient heuristic is proposed based on the additional assumption that each order is picked along its shortest spanning interval, which is the shortest interval that covers all the picking locations of the order. It is shown that the proposed heuristic will produce a solution that is never more than 1 revolution longer than the optimal, i.e., the more orders to be picked, the better the solution.