Order picking is one of the most cost intensive functions in modern warehouses. Efficient storage locations are scarce and expensive and represent a new challenge in developing warehouse systems. Efficient solutions have to be found. Mobile racking systems are thus a good opportunity to improve efficient use of warehouse space as space utilization is optimized. In traditional warehouses aisle space between rack pairs is needed in order to be able to retrieve the stored items. In mobile racking systems the need for aisle space is greatly reduced, thus making it possible to use much more space for storage. Disadvantages of mobile racking systems include the relatively high investment costs, long access times, and low throughput performance. This master's thesis reviews existing literature on typical decision problems in the design and control of the manual order-picking process. An overview of the state of the art of the optimization of mobile racking systems is given. A central point of focus is routing optimization with respect to mobile racking systems employing a single-side picking arrangement and a single command cycle.The warehouse considered is rectangular in shape with a principle front aisle, a moveable picking aisle, and a single order picker.The focus is placed on the optimization of the routing for two different types of mobile racking sys-tems that differ in terms of capacity of the order picking device. In the first case, the order picker can carry only one article (e.g. one pallet). In the second case the order picking device has a capacity of one batch. The aim is to determine the optimal sequence of the retrievals for a given order or batch. The effectiveness of the single-side picking models is demonstrated by means of routing examples developed by the author. Directions for future research are also identified.