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In 1992 a three-year monitoring program was started to assess the quality of the upper groundwater in the sandy regions of the Netherlands as a result of using fertilizers and manure in agriculture. This program is a cooperative effort of the National Institute of Public Health and Environmental Protection (RIVM) and Agricultural Economics Research Institute (LEI-DLO). From march to august 1992 the upper groundwater from 93 farms was sampled and analyzed for chloride, nitrate, potassium, dissolved organic carbon and phosphate (ortho and total). The report contains the monitoring results of the first year of the program. Mean nitrate and potassium concentrations exceed quality objectives, especially under grassland and silage maize on cattle farms. Nitrate and potassium concentrations in the groundwater of arable farms were generally lower than of cattle farms but on average above quality objectives. In the reports to follow a more detailed analyses will be carried out and the monitoring strategy will be evaluated with a view to the desirability of detecting trends in groundwater quality in future.