Eric Braeden

Character: Dr Charles Forbin

Susan Clark

Character: Dr. Cleo Markham

Gordon Pinsent

Character: The President

William Schallert

Character: CIA Director Grauber

Georg Stanford Brown

Character: Dr. John F. Fisher

Willard Sage

Character: Dr. Blake

Alex Rodine

Character: Dr. Kuprin

Martin E. Brooks

Character: Dr. Jefferson J. Johnson

Marion Ross

Character: Angela Fields

Dolph Sweet

Character: Missile Commander

Byron Morrow

Character: Secretary of State

Lew Brown

Character: Peterson

Sid McCoy

Character: Secretary of Defense

James Hong

Character: Dr. Chin

Robert Cornthwaite

Character: First Scientist

Tom Basham

Character: Thomas L. Harrison

Leonid Rostoff

Character: Russian Chairman

Serge Tschernisch

Character: Translator

John Davey

Character: Military officer on phone (uncredited)

Paul Frees

Character: Colossus (voice) (uncredited)

Fred Holliday

Character: Military Computer Entry - Missile Launch (uncredited)

Robert Quarry

Character: Scientist (uncredited)

Don Ross

Character: Logan US Air Force (uncredited)

William Traylor

Character: Party Guest (uncredited)