Application of nitrogen fertilizers have been increased without considering the harmful impacts on soil properties, agricultural products and especially on the environment. As the most common form of nitrogen, nitrate is easily transferred to ground-water resources. Ground-water is the main water supply in arid and semi arid regions, because of good quality and easy availability. The objective of this study was to determine nitrate concentration, distribution and fluctuations in the ground-water around the Zayanderoud River in the arid and semi arid region of Isfahan province. In this way, about 100 functional wells were selected from Baghbahadoran to Varzaneh and the concentration of NO3-N,Cl-, HCO3- K+, Na+, Ca2+, Mg2+, SO2-4, TH and EC were measured monthly from October 1998 to October 2002. The average concentration of NO3-N in Baghbahadoran, Flavarjan, and Varzaneh were 5.5, 17.6 and 6.4 mg/l respectively. The highest value of nitrate nitrogen of 70.8 mg/l (7 times much than standard value of 10 mg/l) was observed in Jalalabad region, one kilometer from Zayanderud River. There was not any significant