The effect of orgotein, the drug version of bovine Cu-Zn superoxide dismutase, on PG production by phagocytosing leukocytes has been investigated. Orgotein inhibited PG formation in a dose/dependent manner. Arachidonic acid was able to reverse this inhibitory effect. In the light of these results it is suggested that anti-inflammatory properties of orgotein may depend, at least in part, on the inhibition of phospholipase activation.