The determination of an optimal feeding and marketing strategy for a beef grazing enterprise is formulated as a dynamic programming problem. It is supposed that a decision has to be made from time to time as to whether to market animals at their current weights or to retain them for further fattening; if the former policy is adopted, a further judgment is required as to whether to purchase replacement cattle immediately or at some later time. To obtain a realistic feeding and marketing model, liveweight gains and saleyard prices are assumed to be dependent on the time of the year and the breed of the cattle, saleyard prices also being dependent on liveweight.