The effect of a 60 day administration of 200 mg heparan sulfate (Hemovasal 100 b.i.d.) or 100 mg mesoglycan (50 mg b.i.d.) was assessed under double blind design in forty patients (thirty-six males and four females) with peripheral occlusive arterial disease with respect to pain-free walking distance and various haemorheological and haemostasiological variables, platelet aggregation and blood chemistry. The pain-free walking distance significantly improved with heparan sulfate (up 67% from baseline 200.0 +/- 22.5 m and up 34%, with mesoglycan from baseline 207.7 +/- 23.4 m). Heparan sulfate significantly stimulated fibrinolysis and reduced platelet aggregability: these findings suggest an action of heparan sulfate on the endothelial cells, thus reducing their thrombogenicity. The results of the study thus confirm the activity of heparan sulfate in peripheral vascular disease, correcting the conditions which constitute the basis of increased thrombotic risk.