ABSTRACT Data envelopment analysis (DEA) is a non-parametric method in operations research for measuring the efficiency of a set of decision making units (DMUs) such as firms with multiple inputs and outputs. Efficiency is the ability to produce the outputs with a minimum input required. Congestion is evidenced when the attainment of maximal output requires a reduction in one or more of the input amounts used. This study measures the efficiency and congestion of 45 Iranian airports in 2008 with considering three inputs such as airport area, runway area and terminal area and there outputs such as the number of operational flights, the number of passengers and cargo handle. The results illustrated that most airports were not profitable and require increasing their outputs significantly. In other words, they require increasing the passenger movement, aircraft movements and cargo handle for being more efficient. Moreover, the study demonstrates that most airports have congestion in their airport area and suggests that those airports should decrease their airport area to increase their efficiencies