Brian Dennehy
Gen. Leslie Groves
David Strathairn
J. Robert Oppenheimer
Michael Tucker
Leo Szilard
Hume Cronyn
James F. Byrnes
Richard Dysart
President Harry S. Truman
Hal Holbrook
Gen. George Marshall
Barnard Hughes
Henry Stimson
John McMartin
Dr. Arthur Compton
David Ogden Stiers
Franklin D. Roosevelt
Anne Twomey
Kitty Oppenheimer
Lawrence Dane
Olek Krupa
Edward Teller
Bernie McInerney
Ken Pogue
Dwight D. Eisenhower
Gary Reineke
Groves's Commanding Officer
Alan Scarfe
John Seitz
Ralph A. Bard
Tony Shalhoub
Enrico Fermi
Ron White
Colonel Nichols
Patrick Breen
Richard Feynman
Vlasta Vrana
Hans Bethe
Lorne Brass
Klaus Fuchs
Michael Sinelnikoff
Lord Rutherford
Timothy Webber
Colonel Lansdale
Harry Strandjofski
Robert Wilson
Lia Sargent
Mrs. Wisnovsky
David Gow
Jack Wisnovsky
Jonathan Wise
Robert Serber
George R. Robertson
Ed Condon
Dee McCafferty
William 'Deke' Parsons
Tom Butler
Captain DeSilva
David Ferry
Army Major
Michael J. Reynolds
Kenneth Bainbridge
Scott Thomson
Chemist
Arthur Holden
Scientist (uncredited)
Romano Orzari
Leo Szilard's Prime Scientist (uncredited)
Ron Frazier
Colonel Pash
John Pielmeier
Seth
Ester Spitz
Trude Weiss
Stephan Balint
Eugen Wigner
Peter Boretski
Albert Einstein
George Popovich
Samuel Goudsmit
Graham Haley
Haakon Chevalier
Kliment Denchev
Michael Polanyi
Diana Fajrajsl
Ilse Polanyi
Michael Farrell
Shapp
Isabelle Mejias
Mrs. Trowbridge
Robert Morelli
T. O. Jones
Jon Baggaley
James Tuck
David Bolt
Harry Gold
Heinar Pillar
Fleischmann
François Klanfer
Haagen Kistiakowski
Joel Miller
George Kistiakowski
Ed McGibbon
William D. Leahy
Nicholas Kilbertus
Paul Tibbets
Joe Cazalet
Air Force Guard
Bob Clout
Alfred MacCormack
Roland Hewgill
Army General
Stan Gibbons
John J. McCloy
Terrence Labrosse
Allan Dulles
Delise Alison
London Pedestrian
Alex Guard
British Jr. Officer
Philip Spensley
British Sr. Officer
Frederick Neumann
Alexander Sachs
Norris Domingue
General Pa Watson
Steve Barry
Los Alamo Scientist (uncredited)
