After the peritoneal macrophages from mice were incubated with different concentrations of calcium channel blockers for 3 h at 37 degrees C, the macrophages were stimulated with opsonized zymosan for 1.5 h at 37 degrees C. The released H2O2 was measured by fluorescence assay. The results showed that verapamil (Ver), nifedipine (Nif), nicardipine (Nic), nimodipine (Nim), and nitrendipine (Nit) reduced the H2O2 release significantly in a dose-dependent manner. The IC50 values (mumol.L-1) were 30, 50, 49, 63, and 92 for Nic, Nif, Nim, Nit, and Ver, respectively. There was slight inhibition of dihydropyridine (Bay k 8644) 10 mumol.L-1 on H2O2 release. When Bay k 8644 at above concentration combined with Ver, Nim, and Nit 25 mumol.L-1, respectively, the inhibitions of Ver, Nim, and Nit on H2O2 release were increased 32%-40%. Above results showed that on the inhibition of H2O2 release, the effects of dihydropyridines calcium channel blockers were greater than that of Ver, and the effects of Nic and Nif were greater than those of Nim and Nit. The acting sitei of Bay k 8644 at high concentration (10 mumol.L-1 and over) was probably different from that of typical calcium channel blockers Nim, Nit, and Ver in macrophages.