AIM: To evaluate the plasma von Willebrand factor (vWF) levels in patients with ulcerative colitis (UC) and to investigate their relationship with disease activity,systemic inflammation and coagulation activation.METHODS: In 46 patients with ulcerative colitis (active in 34 patients), clinical data were gathered and plasma vWF levels, markers of inflammation (ESR, CRP, and fibrinogen) and thrombin generation (TAT, F1+2, and D-dimers) were measured at baseline and after 12 wk of treatment. Plasma vWF levels were also determined in 52 healthy controls (HC). The relationship of plasma vWF levels with disease activity, disease extent, response to therapy, acute-phase reactants (APRs) and coagulation markers (COAGs) was assessed.RESULTS: The mean plasma vWF concentrations were significantly higher in active UC patients (143.38±63.73%) than in HC (100.75±29.65%, P = 0.001)and inactive UC patients (98.92±43.6%, P = 0.031).ESR, CRP and fibrinogen mean levels were significantly higher in active UC patients than in inactive UC patients,whereas there were no significant differences in plasma levels of D-dimers, F1+2, and TAT. UC patients with raised APRs had significantly higher mean plasma vWF levels than those with normal APRs (144.3% vs 96.2%,P = 0.019), regardless of disease activity. Although the mean plasma vWF levels were higher in UC patients with raised COAGs than in those with normal COAGs,irrespective of disease activity, the difference was not significant (141.3% vs 118.2%, P = 0.216). No correlation was noted between plasma vWF levels and disease extent. After 12 wk of treatment, significant decreases of fibrinogen, ESR, F1+2, D-dimers and vWF levels were noted only in UC patients with clinical and endoscopic improvement.CONCLUSION: Our data indicate that increased plasma vWF levels correlate with active ulcerative colitis and increased acute-phase proteins. Elevated plasma vWF levels in ulcerative colitis possibly reflect an acutephase response of the perturbed endothelium due to inflammation. In UC patients, plasma vWF levels may be another useful marker of disease activity or response to therapy.