Anthony Edwards Dr. Mark Greene Actor George Clooney Dr. Doug Ross Actor Sherry Stringfield Dr. Susan Lewis Actor Eriq La Salle Dr. Peter Benton Actor Noah Wyle Dr. John Carter Actor Julianna Margulies Head Nurse Carol Hathaway Actor Abraham Benrubi Jerry Markovic Guest Star Zachary Browne Jake Leeds Guest Star Carmen Argenziano Howard Davis Guest Star Catherine Lloyd Burns Amy Guest Star Amy Ryan Sister Guest Star Ellen Crawford Nurse Lydia Wright Guest Star Yvette Freeman Nurse Haleh Adams Guest Star Christine Harnos Guest Star Gloria Reuben Jeanie Boulet Guest Star Rick Rossovich Dr. John 'Tag' Taglieri Guest Star Kathleen Wilhoite Chloe Lewis Guest Star Michael Ironside Dr. William 'Wild Willy' Swift Guest Star Robert Knott Donny Costanza Guest Star Michael Crichton Executive Producer John Wells Executive Producer