Four cases of intravascular coagulation associated with a state of acidosis in diabetics were observed in 57 patients with diabetic acidosis and 19 with lactic acidosis, in a series of 112 cases of consumption coagulopathy admitted to a department of medical resuscitation. In three cases the coagulopathy was found only on investigation; in one there were clinical and anatomic signs. The coagulopathy may be found either during the phase of recovery from ketoacidosis, or during the course of severe lactic acidosis, particularly during a recurrence of this form of acidosis. In spite of the unfavorable outcome in 3 of the 4 cases, the abnormal findings of coagulopathy reverted toward normal along with successful metabolic corrections. The factors responsible for consumption coagulopathy are acidosis, collapse, generalised systemic reactions and alterations of platelet function, of coagulation, of the balance between fibrin deposition and lysis and of lipid levels, all characteristic of diabetes. The clinical effects of this coagulopathy seldom become apparent but provide a possible explanation of some of the complications of diabetic ketoacidosis, particularly certain hemorrhagic or thrombotic events, as well as certain visceral complications, especially those affecting renal, pulmonary and cerebral areas.