The purpose of this study was to observe the effects of 5-flourouracil on HCT-116 p53 +/- colon cancer cells. In order to investigate the effects of the drug, concentration-dependent assays and time-dependent assay procedures were used. To evaluate the cell viability after being treated with the drug, XTT technique was used. After performing concentration-dependent assays a consequent decrease in cell viability was observed with increase in concentration of the drug. The time-dependent assay showed a gradual decrease in cell viability with increase in time after exposure to the drug. Western blotting technique was performed on the proteins extracted from the samples. Expression of Bak was examined after the cells were exposed to the drug. Results from western blotting technique revealed that Bak protein was initially over-expressed after the cells were treated with 5-Flourouracil for 48 hours and this over-expression of the Bak resulted in apoptosis of cancer cells. Thus, 5-Flourouracil is considered to be an effective chemotherapeutic drug for colon cancer cells partially though the over-expression of Bak protein.