Fenitrothion, propargite, endosulfan and trifluralin were selected as model substances for testing and optimizing the analytical method. Lifetime toxicity and distribution coefficients were considered. In June 1998,1999 and 2000, samples of five Agean Sea coastal area districts (Manisa, Menemen, Ozdere, Tire and Urla regions) were taken. Thirteen samples out of the 79 samples from 50 to 160 m deep wells used for drinking exceeded the European Drinking Water Standard for Nitrate (5OmgIL). Nitrate concentrations were 1 to 120 mg/L. Pesticides were not detected in the samples. Two samples from Tire region showed low trifluralin concentrations due to the pesticide mobility in the unsaturated aquifer. Despite very high nitrate mobility, no infiltration occurs into the soil because of adsorption and/or degradation process. Groundwater quality starts being contaminated by nitrate fertilizer. The high nitrate mobility causes deep groundwater pollution.