Research on the mechanisms of plant defense responses to stress and pathogen attack has attracted much attention in recent years. This increasing interest stems from the fact that the tools of molecular biology w enable us to study the molecular basis of old biological concepts such as host-pathogen recognition (and particularly the gene- for-gene relationship), hypersensitive cell death and systemic acquired resistance. Our kwledge about avirulence and resistance genes, elicitors, signal transduction and genes involved in plant defense is rapidly expanding. Moreover we are just beginning to test in planta the potential of these results for biotechlogical applications, aimed at improving plant resistance to diseases. The 2nd Conference of the European Foundation for Plant Pathology, hosted by the Societe Fran~aise de Phytopathologie , was devoted to Mechanisms of plant defense responses and was held in Strasbourg, France. It brought together over 350 scientists from universities, research institutes and private sectors of 24 countries. Major advances in the areas under study have been reviewed in plenary lectures and are developed in the main articles of this book. Over 160 high-quality posters were presented and are summarized in short articles. Data from outstanding posters, which were discussed after a short oral presentation, are found in extended articles. As a whole the book presents a collection of papers arranged in six sections and reflecting the present day state-of-the-art of research in the field of plant defense reactions.