n this study, external costs due to air pollution in the city of Tehran are estimated for CO2, SO2, NOXand PM pollutants in 1390. In the first step, employing up to down procedure, these pollutants’ emission from oil products, liquid gas and natural gas fuel from transportation, industrial, household and commercial, army and departments, plants and refineries are estimated. Then the external costs due to these emissions have been computed based on presented Expenditure in universal bank and Iran’s environment organization report at 1381. The results show that external costs due to four mentioned air pollutants are approximately 18/06 thousand billion Rials (based on constant prices in 1981) in Tehran city in 1390. The maximum external costs are 83 percent for PM pollutant, 94 percent for transportation and 72 percent for gasoil fuel from point of views of pollutants type, pollutants producing section and the type of fuel consumed, respectively. Also, the total air pollution external costs due to these four pollutants are 0.18 and 0.71 percent with respect to Gross Domestic Production (GDP) of Iran and Tehran,respectively. In this study, realization of external costs is done under the light of Cost Plus method by inflation andexchange rates. In the first approach, external costs are estimated to be 24.88 thousand billiard Rials and in the second approach, they are found to be approximately 66.74 thousand billiard Rials.