OBJECTIVES--(1) To assess if patients with various forms of Raynaud's phenomenon (RP) have abnormal plasma fibrinolysis that may contribute to diminished digital blood flow; (2) to assess whether patients with RP with evidence of endothelial damage have abnormal plasma fibrinolysis; (3) to determine the clinical relevance of abnormalities, if any, in plasma fibrinolysis in patients with RP. METHODS--One hundred and sixty eight patients with significant RP were studied--46 had primary Raynaud's disease (RD), 32 had suspected Raynaud's syndrome secondary to an undifferentiated connective tissue disorder (undifferentiated CTD), 25 had Raynaud's syndrome associated with atherosclerosis (athero RS), and 65 had an underlying connective tissue disease (CTD RS). All attended in the morning after a low fat light breakfast. After a clinical history was obtained, venous blood samples were collected without stasis for assays of plasma fibrinolysis and factor VIII von Willebrand factor antigen (fVIII vWF Ag). Results were compared with those obtained from normal subjects matched for sex and age. As patients with athero RS were significantly older than the other patients with Raynaud's phenomenon, two groups of control subjects were recruited--namely, 'old' and 'young' control subjects. RESULTS--Patients with CTD RS and athero RS had higher concentrations of fVIII vWF Ag (CTD RS median 174.5 range (45-370)% v 100 (38-202)%, p < 0.001; athero RS 182-5 (100-240)% v 100 (50-158)%, p < 0.001). Both had raised fibrinogen (CTD RS 3.25 (1.9-6.8) g/l v 2.4 (1.2-4.2) g/l, p < 0.001; athero RS 3.4 (2.2-6.2) g/l v 2.5 (1.8-3.9) g/l, p < 0.001) and both had diminished fibrinolysis with reduced plasminogen activator activity (CTD RS 79.5 (31-72) mm2 v 92 (37-197) mm2, p < 0.04; athero RS 73 (45-125) mm2 v 98 (41-197) mm2, p < 0.03). Patients with CTD RS also had raised plasminogen activity (3.3 (2.3-5.8) cU/ml v 2.9 (1.5-5.4) cU/ml, p < 0.001). On the contrary, patients with primary RD and undifferentiated CTD had normal fibrinogen and plasma fibrinolysis. Within each patient group, no significant differences in any of the measured variables were found between those who had RP all year and those who had RP in the winter only, those with RP of the hands only and of hands and feet, or those with and without digital ulcers. CONCLUSION--Diminished plasma fibrinolysis is found in patients likely to have endothelial damage (CTD RS and athero RS). These changes are probably a consequence rather than a cause of the disease.