Contamination of soil was investigated in this study from the Tehran Oil refining Co. of Iran. Fifteen soil samples were collected at several points in the Azimabad, 15 km south of Tehran City, Iran. Samples were collected at depths of 0-30 cm. Control samp leswere prepared to determine background levels of soil contamination with petroleum hydrocarbons for comparison with contaminated sites. Total petroleum hydrocarbon (TPH) and poly-aromatic hydrocarbons (PAH) concentrations varied from 101334.0-101367.1 and 25321.1-25876.6 mg kg-1 respectively. The results elevated levels of TPH and PAH contents when compared with the control sample. Soil acidity (low pH of 5.3-5.9) and low electrical conductivity provided evidence of reduced metabolic activities on the affected site. Microbial growth rates for bacteria and fungi expressed as colony forming units were 2.62×109 and 4.14×106 CFU/g soil, respectively for the contaminated and 5.76×109 and 6.83×106 CFU/g soil, for the control treatments respectively. These drastic changes can have impact on the nutrient cycle and prevents the absorption of nutrients by plant root sand lead to a reduction in yield.