Abstract: Defibrotide is a polydisperse oligonucleotide with multiple effects on endothelial cells, which has been developed for the treatment of different vascular disorders. Defibrotide has been used effectively in the treatment and prophylaxis of hepatic veno-occlusive disease. Recent animal models have clearly suggested an antiangiogenic effect and an anticancer activity. Further in vitro and in vivo investigations are needed.