The aim of this study is to investigate the effects of different doses of paclitaxel against in vitro cell proliferation of the human breast cancer cell line MCF-7.MCF-7 cell line was used.It was divided into 4 groups,one control and three experimental.10μg,100μg and 1000μg paclitaxel were applied to the culture medium belonging to each group,respectively.Later,viability and/or proliferation of the cells were determined by MTS test.An increase was observed in the experimental group cells depending on the dose.The average number of cells obtained from the control and experimental groups was 48.4×10^3(±1.6),21.6×10^3(±1.08),17.4×10^3(±1.12)and 11.4×10^3(±0.79),respectively.The decrease in the experimental groups compared to the control group was statistically significant(p<0.05).When the experimental groups were compared,the number of cells at high dose was low and was statistically significant(p<0.05).In our study,the apoptotic effect of paclitaxel was demonstrated in the MCF-7 cell line.We believe that paclitaxel used in the treatment of cancer diseases will contribute to the reliability.