This paper examines the causal relationship between energy use and real GDP for the period 1967-2002 in Iran. The results of Phillips- Perron test indicate that the real GDP and the four categories of energy, i.e. coal, oil, gas, and hydroelectric energy are integrated of order one. Besides, the Johansen — Juselius maximum likelihood co- integration tests imply the existence of Granger causality. The VEC models that have been estimated to test the direction of Granger causality support a unidirectional causality from GDP to energy use in short run.