Large scale, integrated projects have two special features — economics of scale in investments and operating costs and interdependencies of various kinds. The latter include technological, product and factor market interrelations. A mixed-integer, linear programming model is developed to take account of these considerations. The model is described in general terms and illustrated with a case study of a large scale, integrated fertilizer project. Sensitivity analyses relating to capital budget, supply and demand constraints, product and output prices, as well as discount rates are performed to determine the robustness of the model solutions.