We investigated the effects of various sulfur amino acids on the phosphorylation of proteins and the translocation of cytosolic compounds to cell membrane in stimulus-treated human neutrophils using specific monoclonal antibodies. D,L-homocysteine and D,L-homocysteine-thiolactone enhanced fMLP-induced tyrosyl phosphorylation of proteins and the translocation of p47phox, p67phox, and rac to the cell membrane in a concentration-dependent manner. L-cystathionine, NAc-L-cysteine and carboxymethylcysteine suppressed the tyrosyl phophorylation and translocation of cytosolic compounds to the cell membrane. L-cystathionine, L-cysteine and NAc-L-cysteine suppressed PMA-induced serine/threonine phosphorylation and the translocation of cytosolic compounds to the cell membrane. L-cysteine, NAc-L-cysteine and D,L-homocysteine enhanced AA-induced serine/threonine phosphorylation and the translocation of cytosolic compounds to the cell membrane, but L-cystathionine had opposite effects. These results indicated that the effects of sulfur amino acids on tyrosyl or serine/threonine phosphorylation and the translocation of p47phox, p67phox, and rac to the cell membrane in the stimulus-treated human neutrophils were in parallel with those of the stimulus-induced superoxide generation reported in previous paper. L-cysteine, D,L-homocysteine and L-cystathionine weakly inhibited lipid peroxidation, but the other sulfur amino acids tested had no effect.