AbstractIn this paper formulae are derived to give the optimum run lengths on a plant producing two products alternately. The general case ofnruns of one product to one run of the other is considered. The work is applied to a chemical plant and the difficulties of determining certain costs are discussed. It is estimated that appreciable savings can be made.An empirical method of calculating buffer stocks is then described, together with a method of planning production before an annual shut-down. This part of the work does not lead to any substantial savings in cost, but reduces the danger of running out of stock.