Brian Donlevy

as Grant Willard

as Dragon #3

as Gen. Terry Arnold

as George Wellington

as B.D. 'Big Deal' MacPherson

as Henri Delambre

as Tom 'T.P.' Paramutual

as Gen. Sloan

as Doc Bender, Trailhand

as Prof. Bernard Quatermass

as Ed Bates

as Prof. Bernard Quatermass

as Joe McClure

as Charles Quantrill

as Sen. William J. 'Bill' Stephens

as Quantrill

as Nick Palmer

as Walter Williams

as Brigadier General Clifton I. Garnet

as Assistant D.A. Louis D'Angelo

as Maj. Gen. Leslie R. Groves

as Richard Henry Dana

as George Camrose

as Trampas

as Governor McGinty

as Stefan Dubechek aka Steve Dangos

as Dr. Franticek Svoboda

as Lieut. Cmdr. Martin Roberts

as Paul Madvig

as Maj. Geoffrey Caton

as Memphis

as Steely Edwards

as Jim Sherwood

as Angus Duncan

as Grat Dalton

as Daniel 'Dan' McGinty

as Kent

as Ralph Callendar

as Sergeant Markoff

as Sid Campeau

as Barshee

as Gil Warren

as Batiste Duryea

as Ace Martin

as Knuckles Jacoby