The effect of sodium aurothiomalate and triethylphosphine gold on the generation of superoxide radicals by chemotactic tripeptide-activated polymorphonuclear leukocytes has been investigated using a cytochrome C reduction technique. Neither gold compound inhibited the binding of the tripeptide to cells. Sodium aurothiomalate in concentrations ranging from 1 to 100 micrograms/ml produced mild, nonsignificant inhibition of the generation of superoxide radicals. In contrast, triethylphosphine gold at a concentration of 0.25 microgram/ml was associated with a mild enhancement of superoxide radical production, but the enhancement was not statistically significant. At concentrations of 1.25 micrograms/ml and above, there was a profound inhibition of superoxide radical production by these activated cells. Since the products of the respiratory burst, including superoxide, are thought to be inflammatory mediators, it is postulated that the inhibition of superoxide radical generation by gold compounds may be another mechanism by which the compounds modulate their antiinflammatory effects in patients with rheumatoid disease.