Pathogen resistance to fungicides has become a challenging problem in the managing of crop diseases and has threatened the performance of some highly potent commercial fungicides. Worldwide, resistance to more than 100 different active ingredients has been reported. This book compiles information on fungicide resistance over the past three decades on the status, development, and processes involved in the build-up of resistance in pathogens to different groups of fungicides, while also suggesting various measures for managing this problem.