In this work 10 mg/ kg defibrotide was injected (i.v.) to 8 cases with atherosclerosis. Blood samples were taken before and 2 hours after defibrotide administrations. The total protein concentrations in plasma were determined by Lowry method. The protein concentrations were 90.16 ± 9.60 mg/ ml and 96.40± 7.40 mg / ml before and after defibrotide applications respectively. This increase was insignificant. The plasma proteins were also separeted according to their molecular weights by isocratic HPLC. Although some increases on the protein content of all the fractions two hours after a single administration of defibrotide were observed, these increases were statistically insignificant. Keywords :