Roddy McDowall Cornelius Kim Hunter Dr. Zira Bradford Dillman Dr. Lewis Dixon Natalie Trundy Dr. Stephanie 'Stevie' Branton Eric Braeden Dr. Otto Hasslein William Windom The President Sal Mineo Dr. Milo Albert Salmi E-1 Jason Evers E-2 John Randolph Committee Chairman Harry Lauter General Winthrop M. Emmet Walsh Aide Roy Glenn Lawyer (as Roy E. Glenn Sr.) Peter Forster Cardinal Norman Burton Army Officer Tom Lowell Orderly James Bacon General Faulkner Ricardo Montalban Armando John Alderman Marine Corporal (uncredited) Alan Baxter General (uncredited) Jack Berle Secretary of State (uncredited) James Franciscus Brent (archive footage) (uncredited) Robert Gunner Landon (archive footage) (uncredited) Bob Harks Aide (uncredited) Linda Harrison Nova (archive footage) (uncredited) James B. Sikking Control Room Officer (uncredited) Arthur Tovey Official at Briefing (uncredited)