William Hopper

Colonel Robert Calder

Joan Taylor

Marisa Leonardo

Frank Puglia

Dr. Leonardo

John Zaremba

Dr. Judson

Thomas Browne Henry

Maj. Gen. A.D. McIntosh

Tito Vuolo

Commissario Unte

Jan Arvan

Signore Contino - Government Official

Arthur Space

Dr. Sharman

Bart Braverman

Pepe

Don Orlando

Fisherman Mondello (uncredited)

George Khoury

Fisherman Verrico (uncredited)

Darlene Fields

Reporter Reynolds (uncredited)

George Pelling

Reporter Maples (uncredited)

James Dime

Felix Roi, a French reporter (uncredited)

Sid Cassel

Farmer (uncredited)

Ray Harryhausen

Man Feeding Elephant (uncredited)

Noel Drayton

1st Reuters News Correspondent (uncredited)

Rollin Moriyama

Dr. Koruku - Japanese Scientist