Pharmacological mechanisms of benzydamine (Tantum) are studied which are of relevance for the antiinflammatory properties of this non-steroidal antiinflammatory drug (NSAID). Benzydamine most effectively inhibits the generation of reactive oxygen species by murine neutrophils (IC50 1.7 X 10(-5) mol/l). Piroxicam, indomethacin and acetylsalicylic acid are ineffective. Benzydamine, however, does not interfere with xanthine oxidase-dependent superoxide anion radical formation or epinephrine oxidation. The other tested NSAID are as well inactive. The findings confirm the missing cyclooxygenase inhibition of benzydamine (IC50 greater than 10(-3) mol/l), contrary to the other NSAID which are strong (indomethacin IC50 6 X 10(-8) mol/l; piroxicam IC50 2 X 10(-7) mol/l) or moderate cyclooxygenase inhibitors (acetylsalicylic acid IC50 10(-5) mol/l). LTB4 generation via the lipoxygenase is only inhibited by indomethacin (EC50 3.6 X 10(-5) mol/l). Benzydamine appears unique among other NSAID by its relatively strong interference with the generation of reactive oxygen radicals and the lack of cyclooxygenase inhibition.