Superoxide dismutase from breef brain and rat liver was assayed in an enzymatic system,
using xanthine oxidase, and a non-enzymatic system, based on aerobic reduction of nitro-
blue tetrazolium in presence of phenazine methosulphate. The non-enzymatic assay is rapid
and simple and permits simultaneous analysis of many samples. Similar results are found by
the two methods of assay of superoxide dismutase.