Companies survive in saturated markets trying to be more productive and more efficient. In this context, to manage more accurately the finished goods inventories becomes critical for make to stock production systems companies. In this paper an inventory replenishment expert system with the objectives of improving quality service and reducing holding costs is proposed. The Inventory Replenishment Expert System (IRES) is based on a periodic review inventory control and time series forecasting techniques. IRES propose the most effective replenishment strategy for each supply classed derived of an ABC-XYZ Analysis.