Glutathione S-transferase A1 (GSTA1) appears to be primarily involved in detoxification processes, butpossible roles in lung cancer remain unclear. The objective of this study was to investigate the expression andfunction of GSTA1 in lung cancer cells. Real-time PCR and Western blotting were performed to assess expressionin cancer cell lines and the normal lung cells, then verify the A549 cells line with stable overexpression. Localizationof GSTA1 proteins was assessed by cytoimmunofluorescence. Three double-strand DNA oligoRNAs (SiRNAs) weresynthesized prior to being transfected into A549 cells with Lipofectamine 2000, and then the most efficient SiRNAwas selected. Expression of the GSTA1 gene in the transfected cells was determined by real-time PCR and Westernblotting. The viability of the transfected cells were assessed by MTT. Results showed that the mRNA and proteinexpression of A549 cancer cells was higher than in MRC-5 normal cells. Cytoimmunofluorescence demonstratedGSTA1 localization in the cell cytoplasm and/or membranes. Transfection into A549 cells demonstrated thatdown-regulated expression could inhibit cell viability. Our data indicated that GSTA1 expression may be a targetmolecule in early diagnosis and treatment of lung cancer.