Objective: To study the influence of transfecting antisense expression vector of the first subtype of the monocarboxylate transporter (MCT1) gene into lung cancer cells on pHi regulation, lactate transportation and cell growth. Methods: MCT1 antisense gene recombinant vector was introduced into human lung cancer cell line A549 by electroporation. The transfected A549 cells resistant to G418 were selected. Positive clones were examined by using PCR. The changes of intracellular pH and lactate were examined with spec-trophotometric method. Cell growth was studied with cell growth curve. Results: Intracellular pH and lactate were remarkably decreased in the cells transfected pLXSN-MCT1 in comparison with A549 cells without transfection (P<0. 001). The growth of A549 cells transfected pLXSN-MCTl was also inhibited remarkably. Conclusion: MCT1 gene may play an important role in pHi regulation, lactate transportation and cell growth in tumor cells. Objective: To study the influence of transfecting antisense expression vector of the first subtype of the monocarboxylate transporter (MCT1) gene into lung cancer cells on pHi regulation, lactation transportation and cell growth. Methods: MCT1 antisense recombinant vector was introduced into human lung cancer Cell line A549 by electroporation. Positive cell clones were examined by using PCR. Intracellular pH and lactate were remarkably decreased in the cells transfected pLXSN-MCT1 in comparison with A549 cells without transfection (P<0. 001). The growth of A549 cells transfected pLXSN-MCTl was also inhibited remarkably.Conclusion: MCT1 gene may play an Important role in pHi regulation, lactate transportation and cell growth in tumor cells.