In this study, the existence of a long-run relationship among per capita CO2 emission, per capita income, and per capita energy consumption is examined over the period from 1960 to 2007 in order to test the validity of the environmental Kuznets curve. To this end, beside the Johansen cointegration test, the Gregory and Hansen cointegration test which allows for a structural break was used. The results of the Johansen cointegration test shows there is a long-run relationship among per capita CO2 emission, per capita income, and per capita energy consumption. According to the Gregory-Hansen test, the existence of a structural break in 1979 together with the long-run relationship cannot be denied. Thus, long-run and short-run analyses were performed for two different regimes: 1960 to 1978 and 1979 to 2007. The results have revealed that in the long-run, the Environmental Kuznets Curve Hypothesis is valid for both periods.