OBJECTIVE: To determine whether measurement of different markers of endothelial damage, activation of coagulation, and platelet activation might differentiate between patients with primary Raynaud's phenomenon (PRP), limited cutaneous and diffuse systemic sclerosis (lcSSc and dSSc), and healthy control subjects. METHODS: Under carefully controlled conditions, fasting blood was drawn from 19 healthy control subjects, 10 patients with PRP, 17 with lcSSc and nine with dSSc for measurement of the following: von Willebrand factor (VWF) and soluble thrombomodulin as markers of endothelial damage/activation, thromboxane (as thromboxane B2) and beta-thromboglobulin as markers of platelet activation, and tissue plasminogen activator antigen, tissue plasminogen activator activity and plasminogen activator inhibitor-1 (PAI-1) as markers of fibrinolysis. RESULTS: VWF was increased significantly in patients with SSc, and there was also a linear trend for thromboxane and tissue plasminogen activator antigen (in addition to VWF) to differentiate between different subgroups of patients with Raynaud's phenomenon. Patients with dSSc had the highest values. A combined index of VWF and thromboxane showed a highly significant trend across the four groups studied. CONCLUSION: VWF, and to a lesser extent thromboxane and tissue plasminogen activator antigen, are associated with disease severity in patients with Raynaud's phenomenon. Prospective studies are now required to establish if these parameters can be used as markers of disease progression.