Tea extract (TE) has been shown to have anti-tumor properties in a wide variety of experimental systems. We evaluated green tea extract (GTE) as a biochemical modulator for the antitumor activity of cisplatin and doxorubicin in the treatment of human lung cancer A549 cells. Cells were grown in RPMI-1640 medium supplemented with 10% (v/v) heat-inactivated fetal bovine serum and two antibiotics (100 units/mL penicillin and $100;{mu}g$/mL streptomycin). Two types of TE, epigallocatechin galate (EGCG) and GTE, were used in this experiment. The cells were seeded at $1{ imes}10^4$ cells/well in the RPMI-1640 media with or without TE ($100;{mu}g$/mL) and then treated with different concentrations of doxorubicin ($0{sim}14;{mu}g$/mL) or cisplatin ($0{sim}35;{mu}g$/mL). After incubation in 5% $CO_2$ at $37^{circ}C$ for 24 hr, cell viability was determined with a MTT assay. We used a Western blot to detect the influence of EGCG and GTE on the expression of p53 and caspase-3 genes in the A549 cells. A549 cell viability decreased to 15% with a $10;{mu}g$/mL concentration of cisplatin, and to 21% with a $8;{mu}g$/mL concentration of doxorubicin, as measured with the MTT assay. However, pre-treatment of the cells with EGCG ($100;{mu}g$/mL) or GTE ($100;{mu}g$/mL) resulted in decreased cell viability with $6;{mu}g$/mL of cisplatin and $4;{mu}g$/mL of doxorubicin. There was no apparent change in cell viability between EGCG or GTE administration in cisplatin- or doxorubicin-induced cytotoxicity in A549 cells. The levels of p53 and caspase-3 in the A549 cells increased with both EGCG and GTE treatment. We found that GTE could potentially affect cisplatin- or doxorubicin-induced cytotoxicity of A549 cells, which may be useful in the chemotreatment of cancer.