in the present work a fuzzy logic model to preliminary assess the risk of accidental releases of ecotoxic substances in hazard plants has been developed. The methodology is based in three steps, the characterization of the hazardousness of the substance, the delimitation of the soil and groundwater vulnerability and the identification of the protective and preventive measures of the plant. The tool has been tested with a set of storage yards of ecotoxic substances, mainly oil, in the Regione Piemonte area (Italy). The results obtained are in good agreement with the real situation of the surveyed storage yards. Thus, by using this methodology it is possible to preliminary assess the risk from uncertain data. (C) 2007 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.