Models are developed wherein the society, wishing to maxim& the present discounted value of energy output net of pollution cc& and with fixed resources for energy production, must decide what portion of its energy needs will be met by fossil fuel and what portion by nuclear energy. It is shown that the pollution effects of each alternative are as important in de&mining the pattern of energy use as the cost of production of each alternative. Several sets of assumptions about production costs and pollution generation are considered.