In ten POAD patients, 800 mg. of Defibrotide (polideoxynucleotide extracted from mammalian lung, with antitrombotic and fibrinolytic activity) were infused i.v. Blood and plasma viscosity, haematocrit, blood filterability and fibrinogen concentration were controlled, in basal conditions and after one hour from the end of infusion. Haemodynamic parameters: rest flow, peak flow, time to peak flow, half time and total time of reactive hyperemia by means of strain gauge pletismography, were controlled at lower limbs before infusion and after 1 h., 2 h., 6 h., from the end of infusion. The present investigation showed an improvement of rheological parameters and a decrease of total time and half time of reactive hyperemia. These data demonstrate a rheological activity of Defibrotide as well as the fibrinolytic one.