Metal ions such as Ca²⁺, Mg²⁺, or Zn²⁺, are important for many cell functions, for example, signal transduction and the modulation of enzyme activity. The relationship between apoptosis and metal cations, especially Ca²⁺, has been described in many reports. We have investigated the role of metal cations in the regulation of apoptosis in the mouse neuroblastoma cell line, Neuro-2A. When Neuro-2A cells were treated with ethylene diaminetetraacetic acid (EDTA), apoptosis was detected as growth inhibition, DNA fragmentation with a ladder pattern in agarose gel electrophoresis, and nuclear decomposition. However, in case of the treatment with ethylene glycol bis- (β-aminoethyl ether) N, N, N', N'-tetraacetic acid (EGTA), which has a higher chelating specificity for Ca²⁺ than EDTA, DNA fragmentation was not detected. Moreover, the apoptosis induced by EDTA was inhibited by exogenous Zn²⁺. The membrane permeable Zn²⁺ chelator N, N, N', N'-tetrakis (2-pyridylmethyl)ethylenediamine (TPEN) also induced apoptosis of the Neuro-2A cells, and addition of equimolar exogenous Zn²⁺ or Cu²⁺, but not Mn²⁺ or Fe²⁺, prevented TPEN-induced apoptosis. The results suggest that Zn²⁺ may be a key regulator of apoptosis in Neuro-2A cells.