MovieDB

Brian Dennehy

Gen. Leslie Groves

50 81†

David Strathairn

J. Robert Oppenheimer

40 77

Michael Tucker

Leo Szilard

44 81

Hume Cronyn

James F. Byrnes

77 91†

Richard Dysart

President Harry S. Truman

60 86†

Hal Holbrook

Gen. George Marshall

64 95†

Barnard Hughes

Henry Stimson

73 90†

John McMartin

Dr. Arthur Compton

59 86†

David Ogden Stiers

Franklin D. Roosevelt

46 75†

Anne Twomey

Kitty Oppenheimer

37 74

Lawrence Dane

52 84†

Ron Frazier

Colonel Pash

49 64†

Olek Krupa

Edward Teller

42 79

Bernie McInerney

52 89

John Pielmeier

Seth

40 77

Ken Pogue

Dwight D. Eisenhower

54 81†

Gary Reineke

Groves's Commanding Officer

48 84†

Alan Scarfe

42 77†

John Seitz

Ralph A. Bard

51 67†

Tony Shalhoub

Enrico Fermi

35 72

Ester Spitz

Trude Weiss

Ron White

Colonel Nichols

35 64†

Stephan Balint

Eugen Wigner

Peter Boretski

Albert Einstein

59 72†

Patrick Breen

Richard Feynman

28 65

Vlasta Vrana

Hans Bethe

39 76

George Popovich

Samuel Goudsmit

Lorne Brass

Klaus Fuchs

30 67

Michael Sinelnikoff

Lord Rutherford

60 97

Graham Haley

Haakon Chevalier

Kliment Denchev

Michael Polanyi

49 69†

Diana Fajrajsl

Ilse Polanyi

Timothy Webber

Colonel Lansdale

Harry Standjofski

Robert Wilson

29 66†

Lia Sargent

Mrs. Wisnovsky

32 69

David Gow

Jack Wisnovsky

Michael Farrell

Shapp

Isabelle Mejias

Mrs. Trowbridge

27 64

Jonathan Wise

Robert Serber

George R. Robertson

Ed Condon

56 90†

Dee McCafferty

William 'Deke' Parsons

Tom Butler

Captain DeSilva

38 75

Robert Morelli

T. O. Jones

Jon Baggaley

James Tuck

David Bolt

Harry Gold

44 71†

David Ferry

Army Major

37 74

Heinar Pillar

Fleischmann

François Klanfer

Haagen Kistiakowski

Joel Miller

George Kistiakowski

Michael J. Reynolds

Kenneth Bainbridge

49 78†

Ed McGibbon

William D. Leahy

Nicholas Kilbertus

Paul Tibbets

Joe Cazalet

Air Force Guard

Scott Thomson

Chemist

31 68

Bob Clout

Alfred MacCormack

55 77†

Roland Hewgill

Army General

60 69†

Stan Gibbons

John J. McCloy

Terrence Labrosse

Allan Dulles

56 70†

Delise Alison

London Pedestrian

Alex Guard

British Jr. Officer

Philip Spensley

British Sr. Officer

Frederick Neumann

Alexander Sachs

Norris Domingue

General Pa Watson

63 83†

Steve Barry

Los Alamo Scientist (uncredited)

24 61

Arthur Holden

Scientist (uncredited)

29 66

Romano Orzari

Leo Szilard's Prime Scientist (uncredited)