Each chapter is devoted to a separate aspect of biocontrol of plant diseases, and in general the chapters are arranged in order of increasing technical complexity. Since these chapters have been written by independent authors there is the possibility of a slight overlap or repetition of certain statements, but this is difficult to avoid with this sort of organizational structure. One of the chapters deals with the biocontrol of weeds, which some may feel out of place, but it is important to have it as weeds cause enormous losses to agriculture. It is our hope that this book will be useful to all students and researchers in plant pathology, microbial ecology, and mycology.