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