Objective: In this study, we aimed to investigate the apoptotic and cytotoxic effects of different doses of cisplatin administered to colon cancer cells (HT29) for 72 h. Materials and Methods: Cells were treated with different (5-200μM) cisplatin concentrations for 72 hours. Apoptosis was determined using the EtBr- AO staining technique. The mRNA expression levels of BCL2L1, CASP3 and CASP8 were analyzed using the RT-PCR method. Results: Cisplatin had a cytotoxic effect in a dose dependent manner for a 72 h incubation period and the optimum apoptotic dose was found to be 50μM. We found a statistically significant increase in the mRNA levels of all three genes after the 5μM cisplatin treatment compared to control cells (p<0.05). 50μM cisplatin treatment did not lead to a significant difference in BCL2L1 mRNA levels (p>0.05) when compared to the control cells. However, CASP3 and CASP8 mRNA levels rose 2.2 and 3.0 fold respectively (p<0.05) after treatment with the same dose and for the same period. Conclusion: Our results showed that cisplatin effectively induced apoptosis via the caspase cascade signal pathway when it was administered to human colon cancer cells at 50μM for 72 h, and it suppressed the antiapoptotic pathway.