Order picking is an essential part of order processing in warehousing and distribution operations and can be performed using manual, automated, or semi-automated systems. This thesis analyzes two automated systems, which include carousel and AS/RS (automated storage and retrieval system). The main goal of this research is to develop mathematical models to compare the performance of both systems under random and class-based storage assignments. Simulation models are used to validate the reliability of mathematical models. The outputs of mathematical and simulation models are consistent indicating carousel system with class-based assignment has the highest throughput. Economic analysis is used to estimate the payback periods required to convert from manual to AS/RS and carousel systems. The economic analysis shows that converting from manual to AS/RS with class-based assignment has the shortest payback period.