This is a second edition of the book, which presents an overview of the most recent findings in the biology of neutrophils. These cells are critically important for protection against bacterial and viral infections and have been implicated in anti-tumor response. In addition, neutrophils represent a unique model for studying fundamental questions of cellular biochemistry and molecular biology. This book provides a detailed description of signal transduction, generation of reactive oxygen, and mechanisms of migration of these cells. It contains unique information on the neutrophil’s role in viral infectious diseases and cancer. It also presents the recent advances in attempts to improve neutrophil function and use these cells in the treatment of diseases.