Sgt. James Conover / Major Harold Giles
Professor Hebbel / Emmett Balfour
Paul Cameron / Trent
Adam Ballard / Louis Mace
Chief of Staff / Coulter
Coroner Leland / Bill Turner
David Hunt / Dean Radcliffe
Dr. Tillyard / Detective Lt. Runyan
Gen. Benton / Philip Exeter Dundee
Budge / Bert Hamil
Randolph E. Branch / New Sentry
Lt. Rupert Lawrence Howard (uncredited) / James Custer
Lincoln Russell / Ben Fields
Capt. Terrence Ralph Brookman / Harvey Kry Jr.
Chino Rivera / General Juan Mercurio
Aabel / Dr. Block
Navigator Dexter / Policeman
The Mikie / Thetan (uncredited)
Andro / Richard Bellero
Ann Barton / Yvette Leighton
Ann Pearson / Prof. Stephanie Linden
Dr. Sui-Lin / Akada
Dave Crowell / Luis B. Spain
Henry Castle / Galaxy Being (as Wm. O. Douglas)
