The goal of this study was to evaluate the effect of the Na+/H+ exchanger-1 (NHE-1) antisense gene on drug-resistant human small cell lung cancer (SCLC) cell proliferation and apoptosis. A recombinant NHE-1 antisense gene was transfected into drug-resistant human SCLC H446/CDDP cells. Intracellular pH (pHi) was measured with fluorescence spectrophotometry. Cell proliferation was assayed cytometrically, and expression of the apoptosis gene caspase-3 was assayed using immunohistochemistry. Apoptosis and the cell cycles were imaged using a flow cytometer. pHi decreased significantly in transfected cells compared with control cells transfected with an empty vector (6.86+/-0.01 and 7.25+/-0.02, respectively, P<0.01). Cell proliferation began to decrease 48 h after antisense gene transfection, and the expression of the caspase-3 was stronger in transfected cells compared to the control group. The drug resistant exponent was significantly decreased (P<0.01), and there were more cells in G1 in the transfected group compared to the control group (70 and 57%, respectively, P<0.05). The rate of apoptosis in transfected cells was significantly higher than in the control group (12.18+/-1.86 and 2.37+/-0.33%, respectively, P<0.01). The NHE-1 antisense gene was able to induce drug-resistant human SCLC H446/CDDP cells to become acidified and apoptotic, which could provide a novel therapy for multidrug resistance SCLC.