A major problem in the treatment of haemophilia A is the development of inhibitors (antibodies) against factor VIII. We report the case of a newborn male with no family history of haemophilia who developed an intracerebral haemorrhage. On day 10 post-delivery severe haemophilia A was diagnosed and treatment with recombinant FVIII (rFVIII) concentrate was started. Seventy-two hours later the presence of inhibitors was suspected because high doses of rFVIII were required to maintain therapeutic FVIII plasma levels. Days after, the inhibitor was detected. The quick detection of the inhibitor in this newborn haemophiliac allowed us to start the immunotolerance early, without interruption in the administration of rFVIII.