50 Hz and 50 mT magnetic field (MF) with an exposure period of 30 min./day for 15 days was used to enhance the efficiency of a low dose of cisplatin on BALB/C mice. Tumor tissues were evaluated by oxidative stress parameters such as superoxide dismutase (SOD) enzyme activity, malondialdehyde (MDA) and glutathione (GSH) levels. The result shows that treatment with MF and cisplatin decreases the activity of SOD and GSH level and increases the MDA level compared to the treatment with MF or cisplatin alone. In conclusion, these results reveal that MF improves the therapeutic efficiency of cisplatin.