A better understanding of the mechanisms involved in small interference RNA (siRNA) gene silencing opens new horizons for the development of the targeted therapy of malignant and benign diseases. As a research tool, siRNA has proven to be highly effective in silencing specific genes and modulating intracellular signaling pathways. However, systemic delivery of siRNA has been more problematic due to degradation and poor cellular uptake. In order to overcome these limitations, a variety of strategies are being developed including new delivery vehicles and chemical modifications. Here, we review potential approaches for the systemic delivery of siRNA for cancer treatment.