$Na^+-Ca^{2+}$ exchanger (NCX) plays an important role in regulating intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) in various excitable cells as well as non-excitable cells. In hepatocytes, however, the role of NCX under oxidative stress is not well understood. The expression and physiological activity of NCX in isolated hepatocytes were examined by molecular and electrophysiological methods. Pretreatments with antisense oligodeoxynucleotides (AS-oligos) depressed the expression of NCX in hepatocytes as well as physiological activities of NCX, measured by membrane current and increase of intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) due to the reverse mode of NCX in the hepatocytes. In hepatocytes exposed to 0.1 mM hydrogen peroxide ($H_2O_2$), which did not yield an increase in expression of NCX protein, membrane current via NCX and influx of $Ca^{2+}$ through the reverse mode of NCX were significantly increased. These results suggest that the reverse mode of NCX may participate in $Ca^{2+}$ overload in hepatocytes under acute oxidative stress.