Abstract: The mechanism of bisphosphonates in inhibiting bone resorption is clear and they are the standard drugs for treating skeletal complications of malignancy. However, there is an increasing amount of evidence from preclinical research showing that bisphosphonates also exhibit anti-tumor activity, both in vitro and in vivo. They affect tumor cell proliferation, adhesion, and invasion and they exhibit antiangiogenic and immunomodulatory effects. The evidence also shows that when combined with radiotherapy or chemotherapy the effect of bisphosphonates is ehhanced.