David Duchovny as Agent Fox Mulder

Gillian Anderson as Agent Dana Scully

Mitch Pileggi as Assistant Director Walter Skinner

William B. Davis as The Cigarette-Smoking Man

John Neville as The Well-Manicured Man

Martin Landau as Kurtzweil

Jeffrey DeMunn as Bronschweig

Tom Braidwood as Frohike

Blythe Danner as Cassidy

Terry O'Quinn as Michaud

Dean Haglund as Langly

Bruce Harwood as Byers

Armin Mueller-Stahl as Strughold

Lucas Black as Stevie

Christopher Fennell as 2nd Boy

Cody Newton as 3rd Boy

Blake Stokes as 4th Boy

Don S. Williams as Group Elder

George Murdock as 2nd Elder

Michael Shamus Wiles as Black-Haired Man

Darrell Davis as Primitive #1

Carrick O'Quinn as Primitive #2

Tom Woodruff Jr. as Creature #1

Greg Ballora as Creature #2

Ted King as FBI Agent on Roof

Luis Beckford as FBI Agent

Steve Rankin as Field Agent

Gary Grubbs as Fire Captain Cooles

Steven M. Gagnon as Last Agent Out

Larry Joshua as DC Cop

Glendon Rich as DC Cop #2

Gunther Jenson as Security Guard

Scott Alan Smith as Technician

Ian Ruskin as Well-Manicured Man's Valet

Paul Welterlen as Control Room Operator

Joel Traywick as Young Naval Guard

Milton Johns as British Valet

Michael Krawic as 2nd Paramedic

Larry Rippenkroeger as Towncar Driver

Josh McLaglen as Buzz Mihoe

Randy Hall as Windbreakered Agent

T.C. Badalato as Fireman

Amine Zary as Tunisian

David Paris as Pilot

Vanessa Morley as Young Samantha Mulder (archive footage)

Jason Beghe as FBI Man at Bomb Site (uncredited)

Glenne Headly as Barmaid (uncredited)