Endogenous (in the blood) or exogenous stressors can irritate tissues increasing adhesion and activation of neutrophils. This process is known as neutrophilic inflammation and includes the activation of neutrophils. This activation of neutrophils includes the activation of myeloperoxidase (MPO), NADPH oxide-reductase (NOX-2) and inducible nitric oxide synthase (iNOS) with generation of harmful neutrophil extracellular traps (NETs), and a broad range of reactive biochemical species. Oxidative modification can change the structure and function of macromolecules leading to tissue damage and diseases. NETs, MPO, NOX-2 and iNOS, as well as proteases and oxidized macromolecules are useful biomarkers ofdiseases as well as potential therapeutic targets. This book is focused in the latest information about the role of neutrophilic inflammation in the pathogenesis of acute and chronic diseases, as well as novel biomarkers and therapeutic targets. In silico, in vitro, ex-vivo and in vivo experimental studies are comprehensively discussed in light of the most currentinformation in this field.