Breast cancer is one of the important public health problems today and recent treatments have not been found to be very effective for advanced-stage metastatic disease of the breast. In the present study ten 3,4,5- trihydroxybenzohy- drazone derivatives (AR 01- AR 10) were synthesized by two different methods viz. reflux and stirring. It was observed that compounds synthesized by stirring method acquire good yield and require less time in comparison to reflux method. Further cytotoxicity activity performed on two breast cancer cell lines viz. MDA-MB-468 and MCF-7 revealed moderate activity in all compounds at 40 mikrog/mL and 80 mikrog/mL which has the highest in samples AR 01 and AR 10 for both cell lines. Considerably all compounds have shown potent antioxidant activity at 50 mikrog/mL and above concentrations. Tumor in mice treated with compound AR 01 was found to be smaller in comparison to control and AR 10. Findings revealed that compound having electron donating group showed more potent activity against breast cancer cell lines both in vitro and in vivo. Cytotoxicity activity also corelates with QSAR study and showed that compounds having donating group showed positive contribution towards the toxicity. These findings suggest that gallic acid derivatives were potent cytotoxic against breast cancer cell lines and may provide potent therapeutic effects against breast cancer.  Kulcsszavak: Gallic acid derivatives, cytotoxicity, antioxidant, in vivo, QSAR