The novel flavonoid compound 3'-hydroxyfarrerol (IdB 1031) was tested in a number of in vitro experiments in order to ascertain its effects on some functions and products of human phagocytes. We found that IdB 1031 did not depress neutrophil phagocytosis and chemotaxis, whereas at a concentration of 10(-4) M it significantly (p < 0.05) reduced the fMLP-triggered neutrophil production of superoxide anion. At the same concentration, the compound decreased the release of neutrophil elastase and myeloperoxidase from neutrophils (p < 0.05). We also found evidence that IdB 1031 is a non competitive, reversible inhibitor of human neutrophil elastase (Ki 200 microns). Finally, IdB 1031 at the concentration of 10(-5) M significantly reduced the release of tumor necrosis factor-alpha and interleukin-8 from monocytes (p < 0.05). We conclude that, in spite of the moderate activity displayed by IdB 1031, these findings add to our current knowledge on the spectrum of the antiinflammatory activities of flavonoids.