Heparin and coumarins have been the mainstay of anticoagulant therapy throughout our working lives. As we stand on the threshold of a new era of anticoagulants it is timely to look back upon their discovery and development. Both have fascinating stories to tell. Jay McLean claimed to have discovered heparin whilst a medical student, although this is disputed. The story of warfarin leads us from a mysterious haemorrhagic disease of cattle to the development of a rat poison which became one of the most commonly prescribed drugs in history. Many people were involved in both stories and we owe them all a debt of gratitude.