Sgt. James Conover / Major Harold Giles

Ivan Dixon

Professor Hebbel / Bifrost Alien / Emmett Balfour

John Hoyt

Allen Leighton / Paul Cameron / Trent

Robert Culp

Adam Ballard / Louis Mace

Robert Duvall

Chief of Staff / Coulter / First Reporter

Willard Sage

Fred Severn / Coroner Leland / Bill Turner

Jason Wingreen

Dean Radcliffe / David Hunt (as Edward C. Platt) / Mr. Terrence

Edward Platt

Dr. Tillyard / Detective Lt. Runyan

Douglas Henderson

Gen. Benton / Philip Exeter Dundee / Elder of Luminos

Ben Wright

Dr. Paul Pollard / Budge / Bert Hamil

Robert Fortier

Randolph E. Branch / New Sentry

Ted de Corsia

Dr. Williams / James Custer

Dabney Coleman

Harvey Kry Jr. / Capt. Terrence Ralph Brookman

David Frankham

Lincoln Russell / Ben Fields

Philip Abbott

General Juan Mercurio / Chino Rivera

Henry Silva

Dr. Block / Aabel

Kent Smith

Policeman / Navigator Dexter

William Stevens

The Mikie

Janos Prohaska

Andro / Richard Bellero

Martin Landau

Ann Barton / Yvette Leighton

Geraldine Brooks