- Maureen Arthur - Woman Speaker
- Richard Kiel - The Monster
- John Alvin - Dr. Carrie
- Milt Kamen - Gingrich
- John Fiedler - Gordon Spangler
- Henry Jones - Captain Julian Wells
- Lenore Kasdorf - Girl
- George Savalas - Kaz (as Demosthenes)
- Antonio Fargas - Sweetstick Weldon
- Fritz Feld - Waiter
- Severn Darden - Dr. Aaron Pollack
- Michael Strong - Walter Green
- Jimmy Hawkins - Jay Remy
- Philip Carey - Sgt. Mayer
- Val Bisoglio - Victor Friese
- Dick Van Patten - Alfred Brindle
- Randy Boone - Gene the Fiddler
- Elaine Giftos - Nurse Janis Eisen
- Kathleen Nolan - Faye Kruger
- James Griffith - Schwartz
- Bob Hastings - Hallem
- Joshua Shelley - George
- Charles Aidman - Police Captain Leo Winwood
- Len Lesser - Crowley
- Elisabeth Brooks - Natalie - Lab Assistant
- Ramon Bieri - Captain Joe Baker
- Suzanne Charny - Catherine Rawlins
- David Doyle - Cardinale
- Joseph Sirola - Benjamin Sposato
- Phil Leeds - Howard Gough
- Keenan Wynn - Capt. Joe 'Mad Dog' Siska
- John Mitchum - Janitor
- Victor Jory - Charles Rolling Thunder
- Madlyn Rhue - Maria
- J. Pat O'Malley - Caretaker
- Ned Glass - Apartment Superintendent
- Tom Drake - Don Kibbey
- Marvin Kaplan - Delgado
- Army Archerd - Man
- Ruth McDevitt - Elderly Woman
- Ruth McDevitt - Edith Cowels
- Scatman Crothers - Uncle Filemon
- Mary Wickes - Dr. Bess Winestock
- Virginia Gregg - Dr. Hollenbeck
- William Smith - Jim Elkhorn
- John Doucette - Deputy Sample
- Alice Ghostley - Dr. Agnes Temple
- Paulene Myers - Marie Juliette 'Mamalois' Edmonds
- James Gregory - Captain Quill
- Michael Fox - Frank Wesley
- Jan Murray - Ichabod Grace
- Rudy Challenger - Stanley Wedemyer
- Robert Yuro - Detective Webster
- Larry Storch - Swede
- Phil Silvers - Harry Starman
- Murray Matheson - Mr. Lane-Mariot
- Creed Bratton - Man Entering Lab
- Beatrice Colen - Jane Plumm
- Richard Gautier - Mel Tarter
- Ken Lynch - Capt. Warren
- Mews Small - Masseuse
- Rob Berger - Mail Boy
- Roberta Collins - Det. Cortazzo
- Clint Young - Driver
- Mickey Gilbert - The Ripper
- William Daniels - Police Lt. Jack Matteo
- Anne Whitfield - Call Girl
- Noel De Souza - Chandra
- Nita Talbot - Paula Griffin
- Eric Braeden - Bernhardt Stieglitz
- Barry Cahill - Dr. Alan Ross
- Lewis Charles - George Levitt
- Fred Beir - Ryder Bond
- Virginia Vincent - Mrs. Markoff
- Alice Backes - Dr. Shropell
- Carol Ann Susi - Monique Marmelstein
- Carol Veazie - Mrs. Sherman
- Dennis McCarthy - Guard
- Dennis McCarthy - Ballistics Man
- Patricia Estrin - Felicia Porter
- Tom Skerritt - Robert W. Palmer
- Julie Gregg - Susan Driscoll
- Ellen Weston - Lorraine Palmer
- John Myhers - Senator James Talbot
- Jeanne Cooper - Dr. Kline
- William Mims - Officer Hale
- Robert DoQui - Park Policeman
- Dick Patterson - Stephan Wald
- Stanley Adams - Bartender
- Bill Welsh - T.V. Announcer
- David Lewis - Auctioneer
- Johnny Silver - Pepe LaRue - Morris Shapiro
- Brian Avery - Record Producer
- Maurice Marsac - Henri Villon
- Robert Cornthwaite - Dr. Hartfield
- Cy Chermak
- Darren McGavin
James Griffith hace el papel de Schwartz.
Tom Skerritt interpreta a Robert W. Palmer en la serie.
Ken Lynch hace el papel de Capt. Warren.
Phil Leeds interpreta a Howard Gough en la serie.
Stanley Adams hace el papel de Bartender.
Simon Oakland interpreta a Tony Vincenzo en la serie.
Jack Grinnage hace el papel de Ron Updyke.
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