Arthur Hill as Dr. Jeremy Stone

David Wayne as Dr. Charles Dutton

James Olson as Dr. Mark Hall

Kate Reid as Dr. Ruth Leavitt

Paula Kelly as Karen Anson

George Mitchell as Jackson

Ramon Bieri as Major Manchek

Peter Hobbs as General Sparks

Kermit Murdock as Dr. Robertson

Richard O'Brien as Grimes

Eric Christmas as Senator from Vermont

Mark Jenkins as Lt. Shawn (Piedmont team)

Peter Helm as Sgt. Crane (Piedmont team)

Joe Di Reda as Wildfire Computer Sgt. Burk

Carl Reindel as Lt. Comroe

Ken Swofford as Toby (technician)

Frances Reid as Clara Dutton

Richard Bull as Air Force Major

John Carter as MP Capt. Morton

Glenn Langan as Cabinet Secretary (uncredited)

Sandra de Bruin as Technician (uncredited)

Susan Brown as Allison Stone (uncredited)

Bart La Rue as Medic Captain (uncredited)

Walter Brooke as Assistant to Cabinet Secretary (uncredited)

Jan Burrell as Mother - Piedmont (uncredited)

Dee Carroll as Technician (uncredited)

Michael Crichton as Bearded Surgeon (uncredited)

David McLean as Sen. McKenzie (uncredited)

Emory Parnell as Pete 'Old Doughboy' Arnold (uncredited)

Michael Pataki as Operator of 'The Hand' (uncredited)

Quinn K. Redeker as Capt. Morris (uncredited)

Garry Walberg as Technician (uncredited)

Len Wayland as Utah Crash Site Officer (uncredited)

Jason Johnson as Dr. Benedict (uncredited)

Ivor Barry as Murray (uncredited)

Lance Fuller as Man (uncredited)

Don Messick as Alarm (voice) (uncredited)

Joan Swift as Decontamination Receptionist (uncredited)

Alma Platt as Woman (uncredited)

Paul Ballantyne as Hospital Director (uncredited)

Benjie Bancroft as Police Officer (uncredited)

Joe Billings as Scientist (uncredited)

Patty Bodeen as Girl (uncredited)

Michael Bow as MP at Stone's (uncredited)

Duke Cigrang as Father - Piedmont (uncredited)

Rhodie Cogan as Minor Role (uncredited)

Lisa Daniels as Woman (uncredited)

Bill Dunbar as Vandenberg AFB Sergeant (uncredited)

Harold Dyrenforth as Minor Role (uncredited)

Walker Edmiston as Voice (voice) (uncredited)

Sandra Ego as Girl (uncredited)

Don Ellis as Minor Role (uncredited)

Judy Farrell as Pam (uncredited)

James W. Gavin as Dempsey - Helicopter Pilot (uncredited)

Sheila Jo Guthrie as Girl - Piedmont (uncredited)

Robert L. Hughes as Air Force Technician (uncredited)

Jamie Lamb as Boy - Piedmont (uncredited)

Johnny Lee as Boy (uncredited)

Theodore Lehmann as Scientist (uncredited)

Tom McDonough as Stetson (uncredited)

Cliff Medaugh as Civilian (uncredited)

Victoria Paige Meyerink as Minor Role (uncredited)

Midori as Bess - Lab Technician (uncredited)

Carl B. Morrison as Minor Role (uncredited)

Francisco Ortega as Gateman at Agricultural Center (uncredited)

Georgia Schmidt as Old Lady - Piedmont (uncredited)

Reuben Singer as Dr. Rudolph Karp (uncredited)

Gilchrist Stuart as Man (uncredited)

Lorna Thayer as Woman (uncredited)

Gary Waynesmith as Air Force Technician (uncredited)

Russ Whiteman as Civilian (uncredited)