We report a 22 years old male, admitted to the emergency room due to a life threatening coagulation disorder, with prothrombin times fluctuation between 5 and 37% and very low activity of factors II, VII, IX and X. In the month prior to the admission, the patient had used the rodenticide difethialone, without any precaution to avoid accidental exposure. The patient was maintained with fresh frozen plasma until oral vitamin K1 was obtained. This medication corrected the coagulation disorder. (Rev Méd Chile 2000; 128: 647-9).