AbstractThe chemiluminescence of luminol and lucigenin is often used to detect the production of reactive oxygen derivatives by phagocytic cells. Also, several quenchers and enzyme inhibitors are used to determine which oxygen derivatives are responsible for the observed effects. In the present work we have assessed the reliability of dimethylthiourea and cysteamine (OH. quenchers), desferrioxamine (iron chelator) and diethyldithiocarbamate (superoxide dismutase inhibitor). They all react with CIO− and are also strong inhibitors of the luminescence of luminol catalysed by horseradish peroxidase (HRP); cysteamine and diethyldithiocarbamate also react with H2O2. NaN3 is an inhibitor of myeloperoxidase and a quencher of singlet O2, but we found that under certain conditions it can amplify the the luminescence of luminol triggered by CIO− or Fenton's reagent. A complex of copper and penicillamine that had been proposed as an \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm O}_{\rm 2} ^{\bar .} $\end{document} quencher, quenches all luminescent reactions studied. On the other hand, we were able to confirm the relative specificity of other quenchers: taurine for CIO−, benzoate for OH. and mannitol for both OH. and ‘crypto‐OH.’.