Respiratory burst, or the rapid generation of reactive oxygen species from immune cells, is crucial for the destruction of invading microorganisms by phagocytes. During this process, professional phagocytes convert molecular oxygen to superoxide anions through the action of NADPH oxidase, which is then converted to reactive oxygen species with potent antimicrobial activity. Cayman"s Neutrophil/Monocyte Respiratory Burst Assay Kit provides PMA, dihydrorhodamine 123, and additional reagents necessary for inducing and quantifying a respiratory burst response in neutrophils and monocytes by flow cytometry. The assay can be performed on whole blood or on cells in various types of cell culture media. Because the assay reagents are not species-specific, this assay can be used in any species or cell type capable of producing a NADPH oxidase-dependent respiratory burst response.