A new Soil-Groundwater Module has been developed for incorporation in the Dutch Risk Assessment System for New Chemicals. In this module, the exposure of humans and the environment to xenobiotic substances due to sewage sludge application have been determined. Exposure criteria were: 1. accumulation in the uppermost soil layer one year after sewage sludge application, and 2. the maximal substance-concentration of the deeper groundwater. The calculation procedure is incorporated in the menu driven computer program of the Risk Assessment System. For the quantification of the exposure to each new xenobiotic substance the following inputs are needed: - substance characteristics: the sorption coefficient based on organic matter, Kom, and the half-life, DT50-soil, which represent sorption and transformation of the substance, respectively. - the actual substance dose rate on the soil, expressed in kg/ha, which is calculated in the Sewage Sludge Module of the Risk Assessment System. The Kom and DT50-soil should be determined from the n-octanol/water distribution coefficient, Kow, and the Readily Biodegradability test result, respectively.