We report the case of a severe relapsing phenprocoumon-induced hepatitis. The first episode of hepatitis was thought to be caused by another drug (Verapamil). The anticoagulation with Phenprocoumon was therefore continued after healing of liver inflammation. The relapse typically developed after a shorter exposition-time supporting the hypothesis of an allergic etiology. Fortunately we didn't find any cross-reaction between Phenprocoumon and Acenocoumarol. The patient could thus be anticoagulated orally without complications. If long term anticoagulation is absolutely essential, it is reasonable to prescribe a different Coumarin-derivate. In the case of a cross-reaction, the therapy should be continued with low-molecular weight heparin.