J. Robert Oppenheimer
Kitty Oppenheimer
Leslie Groves
Lewis Strauss
Jean Tatlock
Ernest Lawrence
Boris Pash
David Hill
Niels Bohr
Edward Teller
Roger Robb
Frank Oppenheimer
Albert Einstein
Patrick Blackett
William Borden
Kenneth Nichols
Senate Aide
Gordon Gray
Haakon Chevalier
Isidor Rabi
Vannevar Bush
Counsel
Thomas Morgan
Ward Evans
Lloyd Garrison
Senator McGee
Chairman Magnuson
Senator Bartlett
Senator Pastore
Senator Scott
Dutch Student
Werner Heisenberg
Luis Alvarez
Rossi Lomanitz
Hartland Snyder
Robert Serber
Jackie Oppenheimer
Mary Washburn
Barbara Chevalier
George Eltenton
Richard Tolman
Ruth Tolman
Joe Volpe
Congressman
Edward Condon
Donald Hornig
Kenneth Bainbridge
Richard Feynman
Concerned Scientist
Hans Bethe
Kurt Gödel
George Kistiakowsky
Seth Neddermeyer
Enrico Fermi
Klaus Fuchs
Charlotte Serber
J. Ernest Wilkins
Leo Szilard
Lilli Hornig
Lyall Johnson
Philip Morrison
Henry Stimson
George C. Marshall
James Byrnes
James Conant
AAF Officer
Weatherman
Army Captain
Soldier
AAF Officer 2
Burn Victim
Laughing Woman
Kissing Woman
Kissing Man
Weeping Man
Consoling Woman
Presidential Aide
Harry Truman
Lyndon Johnson
Senator's Assistant (uncredited)