In a one year study, nitrate concentrations of superficial ground water were determined in Styria. Of 3931 samples, 21.1% were above 30 mg, 10.1% above 50 mg and 1.5% above 100 mg NO3/1. The contaminated areas lie exclusively in the Styrian tertiary basin, especially in the loose fluvoglacial deposits downstream of Graz. These areas are further characterized by a high population density, intensive cultivation of maize and intensive animal farming (pig breeding). Aside from toxicological aspects, increased nitrate concentrations are an indicator of human influences on the environment, which no longer permit the exclusion of substances potentially deleterious to health in the ground water. The areas are of great interest from the point of view of water supply and distribution because of the great quantities of water to be found there.