An inventory system that consist of two different products is considered in this paper. Demand of these
products have purchase dependent power, i.e. demand of product A is affecting demand of product B, and vice versa.
Then, a vector autoregressive VAR(1) model is being used as the reference forecasting model for the demand
pattern. This forecasting model is being used as a basis for determining inventory policy for two products with
purchase dependent power. An inventory decision model regarding when and how much to order of these products
is developed in order to minimize total inventory cost consists of ordering and holding cost. Possibility to reducing order cost by joining replenishment of these products also being evaluated.