The Joint Research Centre of the European Communities, and in particular the Institute for Systems Engineering and Informatics (ISEI) at Ispra, have weil established competences in risk analysis, uncertainty analysis and statistical data treatment. More recently, work on Environmental Impact Assessment (EIA), particularly on environmental indicators and indices and on a "system engineering approach" to EIA, has started. This approach attempts to move towards "unified" procedures to investigate normal operation and acciclental risks; these are problems concerned within both the EIA Directive 85/337/EEC and the "Seveso" Directive 821501/EEC. In May 1990, a Workshop on "Indicators and Indices for Environmentallmpact Assessment and Risk Analysis" was organized at the JRC, Ispra. The Proceedings of this Workshop (Report EUR 13060 EN, 1990) are a reference document in the fielet This book is based on the papers presented at the Eurocourse EIAl91 held at the JRC, Ispra in the Autumn of 1991. This was the first course on Environmentaiimpact Assessment given in the JRC's Eurocourse series at Ispra. It was a success because of both the high calibre of the lecturers and the weil informed and numerous participants. The work focuses on the broader aspects of EIA, namely: legislation, indicators and indices, approaches and techniques, economic and sociological implications.