Discrete linear control theory is used in this research to examine the effects of system choice and data errors on the performance of production control systems. Two common information flow systems are modelled. These are the Reorder Cycle (ROC) and the Material Requirements Planning (MRP) systems. System choices include the choice of forecasting method, the choice of delivery policy, and the choice of inventory rule. The source of data errors include stock recording errors, delay in stock recording, incorrect bills of material. The other part of the research examines the sequence of implementing a new production control system. Different ways of moving from a Reorder Cycle to a Material Requirements Planning system are studied. Guidelines for an implementation sequence are produced.