Abstract: Concentrations of NO3--N and NO2--N that constitute the main source of ground water and soil contamination, were determined in well and ground water as well as soils in Al-Hassa Oasis. Three analytical procedures were used to determine the concentrations of NO3- and NO2-. There were no significant differences in the analytical results of the methods followed. However, the concentration of NO2- was lower than that of NO3-. Overall, the concentration of NO3- was higher than the critical limits established for plant growth, human health and animal uses. The differences in concentration of these anions were due to differences in the depth of water bearing aquifer and to human activities in the area. The NO3- content in the soil depended on the type of nitrogen fertilizer used. Organic manure and urea fertilizer increased the NO3- in the soil. NO3- increased with increasing soil depth, but was less in the second layer (25-50 cm) of the soil than the upper layer (0-25 cm).