A number of tricyclic antidepressants appear to have inhibitory action on calmodulin. Although amitriptyline, imipramine and doxepine have been shown to inhibit calcium uptake, oxidative phosphorylation and ATPase activities, effects of amitriptyline, imipramine and doxepine on functional responses of human neutrophils have not been elucidated. In this study, effects amitriptyline, imipramine and doxepine on superoxide and hydrogen peroxide generation, myeloperoxidase release, leukocriene B4 formation and intracellular calcium level were investigated. Superoxide and hydrogen peroxide production in heat aggregated IgG-activated neutrophils were inhibited by amitriptyline, imipramine and doxepine. EDTA, EGTA, verapamil and bepredil inhibited heat aggregated IgG-induced superoxide production. Chlorpromazine, trifluoperazine, staurosporine and H-7 also inhibited it. PMA-induced superoxide production was inhibited by amitriptyline, imipramine, doxepine, chlorpromazine and H-7. Amitriptyline, imipramine, chlorpromazine and trifluoperazine inhibited the myeloperoxidase release by heat aggregated IgG. Productions of LTB₄, and 5-HETE in heat aggregated IgG-activated neutrophils were inhibited by amitriptyline, imipramine and doxepine. In neutrophils, elevation of intracellular calcium induced by heat aggregated IgG was inhibited by amitriptyline, imipramine, doxepine, chlorpromazine and EGTA, while verapamil slightly inhibited increase of intracellular calcium and H-7 did not inhibit it. These results suggest that the inhibitory effect of amitriptyline, imipramine and doxepine on respiratory burst, myeloperoxidase release and LTB4 production in heat aggregated IgG-activated neutrophils appears to be ascribed to the inhibition of calcium mobilization, calmodulin and protein kinase C.