Guest stars
Memorable appearances on the show have included:- Bradley Whitford in 1995, as the husband of a woman who dies at the hands of Dr. Mark Greene in a complicated emergency delivery and files a malpractice suit.
- Lucy Liu in 1995, as an Asian Immigrant whose son suffers from AIDS; (credited as "Lucy Alexis Liu").
- Jorja Fox in 1996-1999, as Dr. Maggie Doyle, a gay resident who eventually tried to bring a sexual harassment lawsuit against Dr. Robert Romano.
- Sanford Meisner in 1995, as Joseph Klein, a terminally ill patient inadvertently given a reprieve by Dr. John Carter.
- Marg Helgenberger in 1996, as one of Dr. Doug Ross's many flings.
- George Eads in 1996, as a paramedic.
- Kirsten Dunst in 1996-1997, as a troubled teenager.
- Omar Epps in 1996-1997, as an intern who jumps in front of a train.
- Ewan McGregor in 1997, as a convenience store gunman.
- Mariska Hargitay in 1997, as Cynthia Hooper, a desk clerk that Dr. Mark Greene dates.
- John Cullum in 1997 and 2000, as Dr. Mark Greene's father.
- Rebecca De Mornay in 1999, as a breast cancer survivor.
- Emile Hirsch in 1999, as a teenage alcoholic.
- David Krumholtz in 2000 and 2002, as a schizophrenic who stabs Dr. Lucy Knight and Dr. John Carter, with Liza Weil playing his wife.
- Shia LaBeouf in 2000, as Darnel Smith, a child with muscular dystrophy.
- Lea Salonga in 2001, as Amparo, a lymphoma-stricken mother of a young boy who fell while putting up Christmas lights.
- Jared Padalecki in 2001, as Paul Harris, a car crash survivor.
- Conchata Ferrell in 2001, as Mrs. Jenkins, the mother of a girl injured in a talkshow brawl.
- Michael Gross in 2001-2004, as Dr. John Carter's father, John "Jack" Carter, Jr.
- Zac Efron in 2002, as Bobby Neville, an injured teen.
- Ed Asner in 2003, as a thieving clinician.
- Thandie Newton in 2004, as Kem, Dr. John Carter's love interest from Africa and mother of his stillborn son.
- Cynthia Nixon in 2005, as a stroke victim.
- Kristen Johnston in 2005, as Eve Peyton, a zealous nurse manager.
- John Leguizamo in 2005, as Dr. Victor Clemente, a zealous but troubled attending physician.
- James Woods in 2006, as an ALS-stricken biochemistry professor.
- Stanley Tucci in 2007-2008, as Dr. Kevin Moretti, a brilliant ICU doctor turned troubled ER Chief.
- Reiko Aylesworth in 2007-2008, as Julia Dupree, the hospital chaplin.
- Kari Matchett in 2007-2008, as Skye Wexler, the Acting Chief of Emergency Medicine.
- Hal Holbrook in 2008, as Walter Perkins, a hospice patient who inspires Luka to make a difficult life decision.
- Steve Buscemi in 2008, as Mr. Masterson,a patient who was secretly in witness protection.