Plasma levels of various blood coagulation factors, antithrombin III and plasminogen were measured in 18 patients with end-stage renal disease treated by longterm hemodialysis. The results were compared with those obtained in a group of normal volunteers. Factors XII, IX and II activities were significantly reduced; factors VIII, VII and X levels were increased; and factors XI and V activities and high molecular weight kininogen concentration were comparable to the control group. Antithrombin III activity and concentration were significantly reduced. The mean plasma fibrinogen concentration was normal although levels above and below normal limits were noted in a few patients. Similarly the mean platelet count was normal, although mild thrombocytopenia occurred in several patients and thrombocytosis in one. In conclusion, the present study confirms published results about factor VIII and AT-III, and provides new information on changes of other coagulation factors in uremia treated by long-term hemodialysis.