Cayman's NETosis Assay Kit provides a simple and fast method for studying the process of NETosis ex vivo. Notably, Cayman's NETosis Assay Kit does not depend upon the DNA component of neutrophil extracellular traps (NETs), as DNA release can occur independently of NETosis. In this kit, primary neutrophils are stimulated to release NETs with either PMA or a calcium ionophore (both included). Unbound neutrophil elastase is washed away following NET generation. Following digest of NET DNA by S7 nuclease, the supernatant containing neutrophil elastase is added to a substrate, which is selectively cleaved by elastase to yield a 4-nitroaniline product that adsorbs light at 405 nm. Enough reagents are provided to test 24 sample conditions for NET production, with analysis in duplicate.