The purpose of this study was to investigate the cytotoxicity of iontophoresis treatment using direct current (DC) with or without antibacterial agents. The following antibacterial agents were used: diamine silver fluoride (AgF); sodium fluoride (NaF); and iodine zinc iodide (JJZ). The cytotoxic activity of DC with or without antibacterial agents against human polymorphonuclear cells (PMNs) was evaluated by the 3-[4, 5- dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay. It was noted that DC (2 mA) killed PMNs in a time-dependent manner and the cytotoxicity was enhanced when DC was combined with antibacterial agents. The toxic effect of antibacterial agents was in the order: AgF>JJZ>NaF. The death of PMNs by DC was evaluated by flow cytometry using annexin V-FITC/propidium iodide staining. DC appeared to induce necrosis rather than apoptosis of PMNs. These results suggest that iontophoresis treatment using DC and antibacterial agents may induce necrotic cytotoxicity in host cells around periapical lesions.