Deterioration is defined as damage, evaporation or decay that prevents items from being used for its original purpose. Some examples of items that deteriorate are vegetables, fruits, pharmaceuticals and others. To increase sales, a supplier frequently offers retailers a trade credit period to promote the purchasing amount. There is no interest charge to retailers if the purchasing amount is paid within the credit period, but granting a long credit period from a supplier increases default risk. In this paper, we propose an economic order quantity inventory model for items with Weibull distribution deterioration and demand rate is a positive exponential function of the credit period. We then characterize the retail's optimal ordering period and credit period. Finally, we run numerical examples to illustrate the model and provide some managerial insights.