Plasma fibrinogen chromatography is a method for quantification of high molecular weight fibrinogen complexes (HMWFC), native fibrinogen and other fibrinogen derivatives in plasma. Enhanced formation of fibrin, intravascular coagulation, thrombus formation, etc., are reflected by elevation of plasma HMWFC, and the method distinguishes between subjects with normal and pathological rates of fibrin formation. Serial standard blood coagulation assays, including plasma fibrinogen chromatography, and neurological studies were performed on 220 patients admitted to a stroke unit. Findings from patients with cerebral infarction were compared against those of three control groups: (1) normals, (2) a stroke control group and (3) a stroke risk factor group. Plasma HMWFC findings were significantly (p < 0.001) higher in the stroke risk factor group than in the normals. Plasma HMWFC values were significantly higher (p < 0.001) in the cerebral infarction patients than in any of the control groups, and plasma fibrinogen, plasminogen, alpha1-antitrypsin and alpha2-macroglobulin also were significantly higher (p < 0.001) in the patients. The greater the degree of initial neurological deficit, the greater were plasma HMWFC values (p < 0.001), and high HMWFC values were associated with poor clinical outcome. Plasma HMWFC values were significantly higher (p < 0.001) in patients with intracerebral hemorrhage, subarachnoid hemorrhage and cerebral embolism. These findings document the fact that a high proportion of stroke patients have coagulopathy, characterized by pathological enhancement of fibrin formation.