• 
  Benjamin Whitrow

  Douglas (1 episode, 1974)
• 
  Vernon Dobtcheff

  Bertheim (1 episode, 1974)
• 
  Michael Anthony

  French Doctor (1 episode, 1974)
• 
  Antonia Pemberton

  Marie Pasteur (3 episodes, 1974)
• 
  Robert Lang

  Ignaz Semmelweis (1 episode, 1974)
• 
  Wolfe Morris

  Skoda (1 episode, 1974)
• 
  Donald Bisset

  Hildenbrand (1 episode, 1974)
• 
  Milo O'Shea

  Paul Erlich (2 episodes, 1974)

• 
  Arthur Lowe

  Louis Pasteur (3 episodes, 1974)
• 
  Susan Tebbs

  Olga Metchnikoff (1 episode, 1974)
• 
  Jean Gilpin

  Prostitute (1 episode, 1974)
• 
  Geoffrey Lumsden

  Vulpian (2 episodes, 1974)
• 
  Geoffrey Russell

  Cohnheim (1 episode, 1974)
• 
  James Grout

  Robert Koch (3 episodes, 1974)
• 
  David Troughton

  Viala (1 episode, 1974)

• 
  Roy Brent

  Pathology assistant (1 episode, 1974)
• 
  Jerold Wells

  Biot (1 episode, 1974)
• 
  Geoffrey Toone

  Von Gossler (1 episode, 1974)
• 
  Michael Gough

  Sir Almroth Wright (1 episode, 1974)
• 
  Stephen MacKenna

  Young Bigo (1 episode, 1974)
• 
  Michael Poole

  Cohn (1 episode, 1974)