This book highlights the important role of neutrophils in health as well as in the pathogenesis of various diseases. Section 1 provides a general background information regarding the mechanisms and various triggers of neutrophil extracellular traps (NETs) formation and their role in various infectious and noninfectious diseases (such as postinjury inflammation). Section 2 provides recent evidence regarding the role of neutrophils in the pathogenesis as well as a therapeutic target for selected disease conditions such as periodontal diseases, rheumatoid arthritis, and cystic fibrosis. Section 3 describes the anti-inflammatory properties of neutrophils with focus regarding their role in graft versus host disease. This book provides a wider picture with regard to the importance of this immune cell type in various diseases with focus on one of its recently discovered properties, NETs. Therapeutic targets aimed to modulate neutrophil functions might provide novel approaches in the treatment of various diseases of infectious and noninfectious origin.