text: R Alyson Reed - Judge Conti (3 episodes, season 8)
  Matt Roth - Art Shepherd (4 episodes, season 3)
  Richard Roundtree - Jerry Shaw (5 episodes, season 1)
  Jeremy Rowley - Nurse Erik (2 episodes, season 8)
  John Rubinstein - Principal Hobson (7 episodes, seasons 5-8)
  S
  John Schneider - Richard Watson (4 episodes, season 7)
  Dougray Scott - Ian Hainsworth (18 episodes, season 3)
  Sayeed Shahidi - Charlie James (3 episodes, season 7)
  James Shanklin - Detective Morgan (2 episodes, season 2)
  Mitch Silpa - Jerry (3 episodes, seasons 2-3)
  John Slattery - Victor Lang (14 episodes, seasons 3-4)
  Lois Smith - Allison Scavo (2 episodes, season 7)
  Marla Sokoloff - Claire (3 episodes, season 1)
  Jake Soldera - Benjamin Katz (3 episodes, seasons 5, 7-8)
  Lucille Soong - Yao Lin (7 episodes, seasons 1 and 5)
  Kylie Sparks - Kim (3 episodes, season 3)
  Stephen Spinella - Dr. Samuel Heller (4 episodes, season 5)
  David Starzyk - Bradley Scott (5 episodes, seasons 5 and 8)
  Heather Stephens - Kendra Taylor (2 episodes, season 1)
  Mindy Sterling - Mitzi Kinsky (6 episodes, season 6-7)
  Lindsey Stoddart - Melissa (2 episodes, season 8)
  Elizabeth Storm - Janie Peterson (2 episodes, season 1)