Eric Braeden

Dr Charles Forbin

Susan Clark

Dr. Cleo Markham

Gordon Pinsent

The President

William Schallert

CIA Director Grauber

Georg Stanford Brown

Dr. John F. Fisher

Willard Sage

Dr. Blake

Alex Rodine

Dr. Kuprin

Martin E. Brooks

Dr. Jefferson J. Johnson

Marion Ross

Angela Fields

Dolph Sweet

Missile Commander

Byron Morrow

Secretary of State

Lew Brown

Peterson

Sid McCoy

Secretary of Defense

James Hong

Dr. Chin

Robert Cornthwaite

First Scientist

Tom Basham

Thomas L. Harrison

Leonid Rostoff

Russian Chairman

Serge Tschernisch

Translator

John Davey

Military officer on phone (uncredited)

Paul Frees

Colossus (voice) (uncredited)

Fred Holliday

Military Computer Entry - Missile Launch (uncredited)

Robert Quarry

Scientist (uncredited)

Don Ross

Logan US Air Force (uncredited)

William Traylor

Party Guest (uncredited)