WILLIAM HALSTED is the 19th century surgeon whose name is most frequently associated with the radical mastectomy procedure; however, this type of surgery actually has been performed since the 16th century. THE DEVELOPMENT of radical mastectomy was a long process, and many surgeons over time have contributed valuable insights and alterations to this fundamental treatment for breast cancer. THIS PROCEDURE may be most commonly associated with Halsted because he promoted a meticulous operative technique, synthesized the best points in the techniques suggested by the most famous surgeons of the 19th century, and provided a scientific basis for the performance of radical mastectomy. AORN J 88 (October 2008) 605–608. © AORN, Inc, 2008.