Stuart Whitman as Adm. Michael Matthews

Robert Wagner as Brett

Rosemary Forsyth as Lia Holmes

Robert Colbert as Cmdr. Woody Patterson

Burr DeBenning as Aguila

Susana Miranda as Elena

Paul Stewart as Barton

Whit Bissell as Prof. Holmes

Richard Basehart as The President

Joseph Cotten as Dr. Ziegler

James Darren as Dr. Talty

Sugar Ray Robinson as Capt. Hunter

Charles Dierkop as Quinn

Larry Pennell as Bill Holmes

William Bryant as Capt. Lunderson

Robert Dowdell as Young Officer

Edward G. Robinson Jr. as Dr. Burkson

Sheila Allen as Blonde Woman

Tom Drake as Gen. Putnam

Johnny Lee as Tony

Glenna Sergent as Sally

Ray Didsbury as Security Guard

Erik L. Nelson as Triton Controller

Paul Bradley as Scientist (uncredited)

Brent Dunsford as Technician (uncredited)

George Holmes as Scientist (uncredited)

Victor Toyota as Scientist (uncredited)