Morawitz is mainly remembered for clarifying the role of prothrombin in clotting, but his mature years saw him guide advances in transfusion therapy. He was among the first to describe haemolytic transfusion reactions and to advocate using blood anticoagulated by citrate. He was a talented organiser - founding the Leipzig Donor Centre during increasingly difficult economic and political times. An excellent general physician, his interest in clotting led to clinical work in thrombosis and angina, and the use of quinidine for cardiac dysfunction. Ironically he died of acute myocardial infarction two years after his first attack of angina and coronary thrombosis.