Neutrophils are immune cells with unusual biological features that furnish potent antimicrobial properties. These cells phagocytose and subsequently kill prokaryotic and eukaryotic organisms very efficiently. Impor- tantly, it is not only their ability to attack microbes within a constrained intracellular compartment that endows neutrophils with antimicrobial function. They can unleash their effectors into the extracellular space, where, even post-mortem, their killing machinery can endure and remain functional. The antimicrobial activity of neu- trophils must not be misconstrued as being microbe specific and should be viewed more generally as bio- toxic. Outside of fighting infections, neutrophils can harness their noxious machinery in other contexts, like cancer. Inappropriate or dysregulated neutrophil activation damages the host and contributes to auto- immune and inflammatory disease. Here we review a number of topics related to neutrophil biology based on contemporary findings.