Energy used for fertilizers was estimated as the total of energy used directly in fertilizer factories and that used indirectly through the "backward linkages" in other industries, both those supplying fuels and electricity and those supplying other inputs to the fertilizer factories, and including energy use by and for the marketing· of fertilizers. Direct energy data were borrowed from a.1978 survey by ~he Fertilizer Institute, and indirect energy figures were computed on the basis .of an input-output study for 1967 from the University of Illinois Energy Research Group combined with other economic and energy statistics. The results show average energy consumption for nitrogen fertilizers of 38,000 Btu per pound of N, for phosphate fertilizers of 12,500 Btu per pound of P2o5, and for potash fertilizers of 4,500 Btu per pound of K20. For nitrogen, the comprehensive· estimate exceeds direct energy consumption per unit of nutrient by about one-third, while for phosphate and potash indirect energy consumption is larger than direct energy consumption. Because of the method of estimation, the estimates a.re likely to be on the low side and should remain usable in the near future.