Blood samples from 23 subjects with chronic renal failure and 19 controls were tested using thrombelastography and other hematologic tests. The uremic subjects were divided into two groups, those who had not yet begun maintenance hemodialysis treatments (12 subjects) and those who had (11 subjects). Compared to those from control subjects, the thrombelastograms from the uremic subjects consistently indicate normal clotting times but significantly elevated amplitudes. The increased amplitudes correlate positively in the dialyzed uremic group with both platelet count and fibrinogen concentration and correlate negatively in both uremic groups with hematocrit. Thrombelastography demonstrates a hypercoagulability in these samples in vitro, despite the prolonged bleeding time that commonly occurs in uremic subjects.