Oscar Ratnoff: his contributions to the golden era of coagulation research.

This report describes some of the accomplishments of Oscar Ratnoff, one of the leaders in the field of coagulation research. His career exemplifies the attributes of an accomplished physician–scientist who has excelled in basic and clinical research, teaching and training, and clinical practice. Dr Ratnoff’s discovery of Hageman and Fitzgerald factors and his development of the waterfall hypothesis of coagulation reactions, and the application of these discoveries to clinical medicine are described.