Gold compounds depress phagocytic cell responses, including chemotaxis, and respiratory burst. However, the effects of gold compounds on the function of phagocytic cells are variable according to the preparation of medicine. In this study, effect of tetrachloroauric acid on activated neutrophil responses, including respiratory burst, lysosomal enzyme release and change of intracellular Ca2+ level and on the synthesis of interleukin-8 and granulocyte-macrophage colony stimulating factor by macrophages was studied. This study further examines how gold compounds affect the activation processes. The respiratory burst stimulated by complement C5a, degraded IgG and PMA in neutrophils was inhibited by tetrachloroauric acid. In contrast to C5a and degraded IgG, PMA-stimulated superoxide production was weakly inhibited by tetrachloroauric acid. Staurosporine, genistein, EGTA and verapamil inhibited superoxide and H2O2 production caused by C5a and degraded IgG. PMA-stimulated superoxide production was inhibited by staurosporine but was not affected by genistein. Tetrachloroauric acid, genistein, EGTA and verapamil inhibited the release of acid phosphatase and myeloperoxidase, while the effect of staurosporine was not detected. The synthesis of interleukin-8 and granulocyte-macrophage colony stimulating factor by interleukin-1β in macrophages was inhibited by tetrachloroauric acid. Preincubation with tetrachloroauric acid, genistein, EGTA and verapamil, the elevation of [Ca2+]i evoked by C5a was inhibited. Store-regulated Ca2+ entry in thapsigargin-pretreated neutrophils was decreased by the addition of tetrachloroauric acid and genistein. The effect of staurosporine on intracellular Ca2+ mobilization was not observed. In conclusion, tetrachloroauric acid may suppress neutrophil responses through its inhibitory action on elevation of intracellular Ca2+ level and protein kinase C. It might exhibit an inhibitory effect on the action of protein tyrosine kinase. Tetrachloroauric acid depresses cytokine production by macrophages.