Blood coagulability in patients following cerebral infarction was studied utilizing the thromboelastograph (TEG). Cerebral infarction patients from two separate institutions were studied within 24 to 48 hours after onset of stroke. Ninety-four stroke patients from one institution and 109 from another yielded a total stroke population of 203 patients for this study. Fifty-nine age-matched normals were used as a control group. Frequency distribution curves were determined for a TEG ratio of ma/(r + k). The 59 controls exhibited a normal frequency distribution between the values of 1.6 and 4.0. Both groups of stroke patients revealed an increased number of patients with a ratio exceeding 4.0, suggesting a hypercoagulable state exists following cerebral infarction in approximately 29% to 38% of the patients studied.