The effect of Ni (II) ions on macrophages is not well understood. The purpose of this study was to examine the dose-dependent effects of Ni (II) ions up to 1,000 micromol/L on production of three inflammatory cytokines (TNF-alpha, IL-1beta and IL-6), superoxide dismutase (SOD) and nitric oxide (NO) by murine macrophage-like RAW264 cells with (+) or without (-) lipopolysaccharide (LPS) -stimulation. Ni (II) ions caused LPS (-) RAW264 cells to slightly increase production of TNF-alpha and IL-6, proportionally to the Ni (II) ion concentration while IL-1beta was not produced, and to slightly increase production of SOD and NO. It can be concluded that Ni (II) ions dose-dependently increased the inflammatory and oxidative stress conditions of LPS (-) RAW264 cells. LPS-stimulation caused RAW264 cells to produce in abundance the three inflammatory cytokines, SOD and NO. Ni (II) ions dose-dependently reduced the three cytokine quantities and NO amounts in LPS (+) RAW264 cells, while dose-independently increasing SOD amounts. It was noted that Ni (II) ions dose-dependently reduce the resistance power against bacteria of LPS (+) macrophages, because the production of volatile NO--bacteria killer is diminished proportionally to the Ni (II) ion concentration.