We found that K(+)/Cl(-) co-transporter 2 (KCC2) activity, monitored with wide-field fluorescence, was inhibited by intracellular Zn(2+), a major component of neuronal injury. Zn(2+)-mediated KCC2 inhibition produced a depolarizing shift of GABA(A) reversal potentials in rat cortical neurons. Moreover, oxygen-glucose deprivation attenuated KCC2 activity in a Zn(2+)-dependent manner. The link between Zn(2+) and KCC2 activity provides a previously unknown target for neuroprotection and may be important in activity-dependent regulation of inhibitory synaptic transmission.