We report the clinical experience of a large Haemophilia Centre and Haemostasis Unit in reversing oral anticoagulation (OAC) using clotting factor concentrates. This is a retrospective study extending over 2 years (January 1996-December 1997). Reversal was performed using a combination of factor IX and factor VII concentrates administered by intravenous infusion. in a dose varying between 12 i.u./kg and 50 i.u./kg. We identified 20 episodes of OAC reversal in 18 patients, with a prevalence of 10 reversal episodes/1000 OAC patients/year. The median age was 77 years old (range 53-92 years). Indications for OAC reversal were divided into major bleeds (muscle haematoma [9], haematuria [3], subarachnoid haemorrhage [1], oesophageal bleeding [1], haemoptysis [1], haemarthrosis [1]); minor bleeds (extensive bruising [9], epistaxis [3], oral cavity bleeding [1]); and emergency invasive investigation (2). Pre-reversal, the international normalized ration (INR) was greater than 6.0 in 15/18 patients. Post-infusion. there was an immediate reduction in the INR towards normal (mean 1.3; range 1.1-2.3). There were no thrombotic complications or other adverse effects. The median use of factor 9 A concentrate was 2300 units/patient (range 570-4195), at a cost of 645 Pounds/patient and for factor VII concentrate 2200 units/patient (range 815-3630), at a cost of 664 Pounds/patient. Clotting factor concentrates provide a safe, rapid and effective means for OAC reversal and although expensive it is the treatment of choice in the over anticoagulated, bleeding patient.