P. T. N. SPENCER-PHILLIPS Co-ordinator, Downy Mildew Working Group of the International Society for Plant Pathology University of the West of England, Coldharbour Lane, Bristol BS16 1QY, UK Email: peter.spencer-phillips@uwe.ac.uk It is a very great privilege to write the preface to the first specialist book on downy mildews since the major work edited by D. M. Spencer in 1981. The idea for the present publication arose from the Downy Mildew Workshop at the International Congress of Plant Pathology (ICPP) held in Edinburgh in August 1998. Our intention was to invite reviews on selected aspects of downy mildew biology from international authorities, and link these to a series of related short contributions reporting new data. No attempt has been made to cover the breadth of downy mildew research, but we hope that further topics will be included in future volumes, so that this becomes the first of a series following the five year ICPP cycle.