Returns caused by the delivery of incorrect items constitute a major problem for non-automated warehouses. Returns not only create extra costs, they also aggravate customers. Most errors in logistics occur during the picking process. MICA — a mobile assistance system for warehouse workers — unobtrusively navigates the worker on his way through the warehouse and effectively prevents picking errors using RFID technology. Therefore, MICA reduces error rates, job training periods, and the time required for picking and packing, leading to lower costs for warehouse operators and increased customer satisfaction. In this paper you will read about a case study where the MICA prototype was field-tested in the warehouse of a medium-sized enterprise. Categories and Subject Descriptors J.7 [Computers in Other Systems]: Process control; H.5.2 [User Interfaces]: Interaction styles General Terms Economics, Human Factors, Management, Performance Keywords Assistance system, RFID, Navigation, Indu...