Alan Alda (recurring) played Dr. Gabriel Lawrence physician reputed to be a founding father of emergency medicine. Lawrence is forced to resign when he confesses he is taking medication for early Alzheimer's disease and he realizes he can no longer practice medicine.




Bradley Whitford played a husband who loses his wife in childbirth. ("Love Labor's Lost")




Chad Lowe portrayed Dr. Carter's student, George Henry.




Djimon Honsou played a Nigerian hospital worker, Mobalage, who faced a deportation hearing for forging his visa. After being granted amnesty, Mobalage pursued a civil engineering license and left his job at the hospital.




Ewan McGregor played a teenager named Duncan who robs a store that Nurse Hathaway is in. During a shootout with the police, Duncan is shot and killed. ("The Long Way Around")




Francis Sternhagen played Dr. Carter's grandmother, Millicent, who supported Nurse Hathaway's idea for a clinic. Millicent took away Carter's trust find when she learned he was hiding his cousin Chase's drug addiction that left Chase in a coma.




Glenne Headly played pediatric surgeon, Dr. Abby Keaton.




John Cullum played Dr. Greene's father a retired naval officer.




Kirsten Dunst played streetwise 14-year-old, Charlie who was befriended by Dr. Ross.




Lisa Nicole Carson played Carla Harris, mother to Dr. Benton's son Reese.




Rosemary Clooney played the mysterious Madame X who can only express herself in song. ("Going Home")




Rebecca de Mornay played Elaine Nichols, the former wife of one of Dr. Carter's cousins, who is treated for cancer.




Ron Eldard played paramedic, "Shep" Shepherd who was romantically involved with Nurse Hathaway. Shep's partner dies in a burning building.




Sally Field played Abby Lockhart's impulsive mother, Maggie Wyczenski. Maggie suffers from bipolar disorder but refuses to take her medication.