The influence of isoquinolinesulfonamides (H‐7 and H‐8), phenothiazines(trifluoperazine and fluphenazine), and a naphthalenesulfonamide (N‐(6‐aminohexyl)‐5‐chloro‐1‐naphthalenesulfonamide (W‐7)) on stimulated superoxide anion production and phosphatidyl inositol (PI) cycle activity was investigated in the guinea pig alveolar macrophage. All five drugs were able to inhibit superoxide anion production stimulated by n‐formyl‐nel‐leu‐phe (FNLP), leukotriene B4 (LTB4), and phorbol‐12,13‐dibutyrate (PDB). The order of potency was trifluoperazine ≥ fluphenzine > H‐7 = W‐7 > H‐8. The dose response curves could be shifted to less efficacy by increasing extracellular calcium. By itself, W‐7 markedly stimulated 45Ca+2 efflux, efflux, fluphenazine and trifluoperazine slightly stimulated 45Ca+2 efflux from macrophages preloaded with 45Ca+2. Consistent with these results, W‐7 markedly stimulated PI cycle activity, fluphenazine and trifluoperazine slightly stimulated PI cycle activity, while H‐7 and H‐8 had no significant effects on PI cycle activity. In addition, W‐7 by itself was able to stimulate a weak and short‐lived “burst” of superoxide anion production. In order to evaluate whether a site of action of the inhibitors was at protein kinase C and whether protein kinase C was involved in terminating the normally short‐lived FNLP‐ and LTB4‐stimulated macrophage activation, fluphenazine and H‐7 were used to evaluate the duration of FNLP‐ and LTB4‐stimulated PI cycle activity, at concentrations of the inhibitors that significantly blocked stimulated superoxide anion production. In all cases, FNLP and LTB4 still stimulated PI cycle activity, which still terminated even though protein kinase C was inhibited. These results suggest that all five drugs block protein kinase C, but H‐7 was the most specific in its action at protein kinase C, while the phenothiazines and W‐7 have multiple sites of action. In addition, these results suggest that protein kinase C may not function to cause the termination of FNLP‐ and LTB4‐stimulated PI cycle activity and subsequent superoxide anion production.