The delay time and chemiluminescence (CL) intensity in delayed-luminol CL catalyzed by copper(II) were remarkably affected by the presence of such metal ions as Cr(III), Mn(II), Co(II), and Ni(II). The variation of the delay time could be explained in terms of the effects of the metal ions on the oxidation rate of cysteamine by Cu(II). Meanwhile, all of the metal ions reduced the CL intensity compared with that by Cu(II) alone. This result could be ascribable to a deactivation of Cu(II) by the metal ions for the decomposition of hydrogen peroxide, thus decreasing the CL emission due to the peroxidation of luminol.