Background and Objectives: There are many problems in treatment of different kinds of tumors. Many studies were carried out for finding suitable antitumor materials in different countries. The aim of this study is to evaluate the antitumor effects of olive and green tea extracts on human breast tumor cell line (BT474).

 Methods: Water and ethanol extracts of green tea and olive were prepared. BT474 cells were treated with determinded concentration of extracts at different incubation times and cell lysis was measured using the lactate dehydrogenase enzyme assay. Experiments were repeated 3 times and the results expressed as means ± standard deviation. Statistical analysis were performed by t-test and p ≤ 0.05 considered as significant .

 Results: Increasing the concentration of green tea in 8 and 24 h exposures decreased cell lysis or killing percentage of treated cells. Olive extract in 1mg/dL concentration showed highest percent (85%) of cell lysis. Cell lysis effect of olive extract treatments was dose-dependent and increased in higher concentrations. There were no significant difference in killing effect of olive extract between 8 and 24 h incubation time (consequently 83% and 85%). But at the same incubation periods the difference between percent of cell lysis in the presence of green tea extracts (0.01 and 0.1 mg/dL) was significant. (p =0.000).

 Conclusions: Our results indicated that crude olive and green tea extractions have exerted lytic effects on BT 474 lines. Olive extract have higher cytotoxicity than green tea. Cytotoxicity of olive extract was dose-dependent .