In 2005 about 1% of the French population could benefit from an anticoagulant treatment by antivitamin K. The hemorragic accidents due to these tretments are frequent. They would be responsible for 17,000 hospiializations and 4 to 5,000 deaths per year. This iatrogen risk could seriously dirninish if the patients had a better knowledge of their treatment. We made a study in the hospital of Saint Dié des Vosges, airning at evaluating 54 patients about their knowledge conceming the treatment by antivitamin K and at measuring the impact of a session of therapeutic education.The study highlights significant gaps. 33.3% of the patients en unaware of the name of their treatment. 66.9% cannot quote an unadvisable medicinal interaction. The monitoring book is used by only 35.2% of the patients. A session of 15 minutes' individual therapeutic education proved insufficient to increase their practical knowledge significantly.Improving therapeutic education seems to be a real need and it concems al1 the actors in charge of the health system : general practtioners, cardiologists, physicians, biologists... The developpement of teaching structures in the prescibing hospital wards as well as in the city hospital network can be part of it.