A single-item inventory model with probabilistic demand is considered in this paper. The replenishment of items is cyclical and occurs every n-periods. The order for replenishment can be p laced at the end of any period during the cycle . The uni ts ordered fluctuate based on actual and expected demand during the cycle. The general expression of this inventory system is formulated by developing the stationary distribution of the inventory position, units ordered and the probability of placing an order during any period. The expression is stated in terms of the reorder point (s) and the order level (S).