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

Darlene Fields

Reporter Reynolds (uncredited)

James Dime

Felix Roi, a French reporter (uncredited)

Ray Harryhausen

Man Feeding Elephant (uncredited)

Noel Drayton

1st Reuters News Correspondent (uncredited)