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)