To determine the mechanism underlying 5-FU-induced alteration of BAX and Bcl-2 genes, we conducted RT-PCR analysis of breast cancer cells after serial diluted 5-FU treatment (0.5, 1.0, and 5.0 μg/ml), and total RNA was extracted at 3, 6, 9, and 24 h. This evidence concerns the gene BCL2 and breast cancer.