When Abraham Pais passed away, his manuscript on Oppenheimer was about three-quarters complete. It cut off on the morning of the first day of Oppenheimer's hearing following the revocation of his security clearance. Pais's widow, Ida Nicolaisen, and Kirk Jensen, an editor at Oxford University Press, asked me to add just enough material to flesh out the story into a com- plete biography, keeping my own contributions to a minimum and leaving Pais's manuscript intact. I therefore composed short chapters on Oppenheimer's hear- ing, on reactions to the hearing, on Oppenheimer's life and work after trial, and on the year of his death. Wherever I could, I quoted from the notes Pais made after his conversations. I tried to steer the narrative toward material that Pais thought important, as indicated by markers or notes in the margins of books, and folders with his handwritten thoughts and notes from interviews— many on yellowing pages, some on the backs of pages which Pais, wearing his physicist's hat, had scribbled equations. I tried to identify Pais's citations of secondary sources, which were not always indicated in the draft manu- script. I noted certain places where, in preparing this ambitious and de- manding work, he had paraphrased the secondary literature he found most valuable, passages that he would no doubt have rewritten in the final ver- sion. I have attempted to locate and provide citations for each of these, though some cases may have escaped notice.