• 
  Mia Farrow

  Allison MacKenzie  (224 episodes, 1964-1966)
• 
  Leslie Nielsen

  Dr. Vincent Markham  (18 episodes, 1965)
• 
  Nichelle Nichols
• 
  Patrice O'Neal

  Rodney Harrington (233 episodes, 1964-1966)
• 
  Ted Hartley

  Rev. Jerry Bedford (12 episodes, 1965-1966)
• 
  Christopher Riordan

  Jeremy  (2 episodes, 1965-1966)
• 
  Judy Pace

  Lillian Walters (1968-1969)  (unknown episodes)
• 
  Dabbs Greer

  E.J. Taggart (2 episodes, 1965)

• 
  Eleanor Audley

  Miss Marsh (1 episode, 1965)
• 
  Susan Oliver (I)

  Ann Howard (48 episodes, 1966)
• 
  Ed Nelson (VI)

  Dr. Michael Rossi (229 episodes, 1964-1966)
• 
  Bill Douglas (I)

  Mr. Scott (1 episode, 1966)
• 
  Myron Healey

  Detective Blaine (2 episodes, 1965)
• 
  Tim O'Connor

  Elliot Carson (181 episodes, 1964-1966)
• 
  Pat Ryan

  Rodney Harrington (233 episodes, 1964-1966)

• 
  Wilfrid Hyde-White

  Martin Peyton (1967) (temporary replacement) (unknown episodes)
• 
  Whit Bissell

  Calvin Hanley (6 episodes, 1965)
• 
  James Doohan

  Thomas (19 episodes, 1965-1966)
• 
  Gregory Morton

  William 'Robert' Wainwright  (9 episodes, 1965)
• 
  Rose Hobart

  Mary (1 episode, 1966)
• 
  Paul Langton

  Leslie Harrington (137 episodes, 1964-1966)
• 
  Joe Maross

  Fred Russell (unknown episodes, 1968-1969)
• 
  Fred Draper

  Bartender Fred (1 episode, 1966)
• 
  Alberta Nelson

  Nurse (1 episode, 1964)
• 
  Ryan O'Neal

  Rodney Harrington (233 episodes, 1964-1966)
• 
  Ruth Warrick

  Hannah Cord (62 episodes, 1965-1967)
• 
  Myrna Fahey

  Nurse Jennifer Ivers (unknown episodes)
• 
  Charles Seel

  Conductor (1 episode, 1964)
• 
  Bruce Gordon

  Gus Chernak (25 episodes, 1965-1966)
• 
  George Macready

  Martin Peyton (72 episodes, 1965-1968)
• 
  Joan Blackman (I)

  Marian Fowler (16 episodes, 1965-1966)
• 
  Joyce Jillson

  Jill Smith Rossi (unknown episodes, 1968)
• 
  Barbara Parkins

  Betty Anderson  (207 episodes, 1964-1966)
• 
  Joan Van Ark

  Nurse Paula (unknown episodes, 1968)
• 
  John Kerr

  District Attorney John Fowler (59 episodes, 1965-1966)
• 
  Kimberly Beck

  Kim Schuster (33 episodes, 1965-1966)
• 
  Grant Gee

  Stella Chernak (71 episodes, 1965-1966)
• 
  Leigh Taylor-Young

  Rachel Welles (unknown episodes, 1966-1967)
• 
  Mariette Hartley

  Dr. Claire Morton (30 episodes, 1965-1966)
• 
  Greg Morris

  Officer Frank (5 episodes, 1965-1966)
• 
  Ruby Dee

  Alma Miles (unknown episodes, 1968-1969)
• 
  Bert Remsen

  Detective Lawrence (4 episodes, 1965-1966)
• 
  Heather Angel

  Mrs. Andrea Dowell (5 episodes, 1965-1966)
• 
  Amzie Strickland

  Lucy Frisby (1 episode, 1965)
• 
  Lee Grant

  Stella Chernak (71 episodes, 1965-1966)
• 
  Barbara Rush

  Marsha Russell (unknown episodes, 1968-1969)
• 
  Roy Roberts

  Sherwood Price (unknown episodes)
• 
  Micky Dolenz

  Kitch Brunner (3 episodes, 1965)
• 
  Victor Izay

  Count Clerk  (2 episodes, 1966)
• 
  Percy Rodrigues

  Dr. Harry Miles (unknown episodes, 1968-1969)
• 
  Jack Dodson

  Al Pearson (1 episode, 1965)
• 
  Don Gordon

  Richard Jensen (5 episodes, 1966)
• 
  Warner Anderson

  Matthew Swain (63 episodes, 1964-1965)
• 
  Steve Oliver

  Lee Webber (50 episodes, 1966-1968)
• 
  Dorothy Malone

  Constance MacKenzie Carson  (187 episodes, 1964-1966)
• 
  Lola Albright

  Constance MacKenzie Carson (8 episodes, 1965-1966)
• 
  Jim Begg

  Arthur Crain (1 episode, 1966)
• 
  Dan Duryea

  Eddie Jacks (unknown episodes, 1967-1968)
• 
  Edith Atwater

  Grace Morton (11 episodes, 1964-1965)
• 
  David Canary

  Dr. Russ Gehring (26 episodes, 1965-1966)
• 
  Patrick O'Neal

  Rodney Harrington (233 episodes, 1964-1966)
• 
  Christopher Connelly

  Norman Harrington
• 
  James Douglas

  Steven Cord
• 
  Patricia Morrow

  Rita Jacks Harrington
• 
  Ed Nelson

  Michael Rossi