We investigated that Hwao-tang had various effects on stimulus-induced superoxide generation in human neutrophils. Hwao-tang significantly inhibited N-formyl-methionyl-leucyl-phenylalanine-induced superoxide generation in a concentration-dependent manner, but not that induced by arachidonic acid. Also, Hwao-tang significantly reduced mouse paw oedema induced by carrageenan. The results suggest that protein tyrosine kinase participates in fMLP-mediated superoxide generation by Hwao-tang-treated human neutrophils. Also, the results indicate that Hwao-tang exerts anti-inflammatory effects related to the inhibition of neutrophil functions and of NO and prostaglandin E2 production, which could be due to a decreased expression of iNOS and COX-2.