Doctors
-Dr Mark Greene (Chief Resident, Series 1+) - Anthony Edwards
-Dr Doug Ross (Paediatrician, Series 1+) - George Clooney
-Dr Susan Lewis (Second Year Resident, Series 1 to 3 Episode 8) - Sherry Stringfield
-Dr Peter Benton (Second Year Surgical Resident, Series 1+) - Eriq La Salle
-Dr Morgenstern (Chief Surgeon, Series 1+) - William H. Macy
-Dr John Tagliari (Orthopod) - Rick Rossovich
-Dr Div Cvetic (Psychiatrist) - John Terry
-Dr Sara Langworthy (Surgeon) - Tyra Ferrell
-Dr Jack Kayson (Cardiologist) - Sam Anderson
-Dr Angela Hicks (Attending Surgeon Series 1 episode 9) - CCH Pounder
-Dr William 'Wild Willy' Swift (Chief Surgeon) - Micheal Ironside
-Dr Carrie Weaver (Resident, Series 2+) - Laura Innes
-Dr Carl Vucelich (Vascular Surgeon, Series 2) - Ron Rifkin
-Dr Maggie Doyle (Resident, Series 3+) - Jorjan Fox
-Dr Abby Keaton (Paediatric Surgeon, Series 3) - Glenne Headly
-Dr Greg Fischer (Infectious Diseases, Series 3) - Harry J. Lennix
-Dr Dennis Gant (Surgical Intern, Series 3. Dies when hit by a train.) - Omar Epps
-Dr Donald Anspaugh (Chief of Staff, Series 3+) - John Aylward
-Dr Karubian - The sleeping Doctor that Carter wakes on his first night as a Doctor. We
    don't see his face but it's David Schwimmer (Ross from Friends)
-Dr Anna Del Amico (Paediatrician specialising in Emergency Medicine, Series 4) - Maria Bello
-Dr Elizabeth Corday (Surgeon, Series 4) - Alex Kingston
-Dr Neal Bernstein (Head of Paediatrics) - David Spielburg
-Dr Janet Coburg (Obs and Gynae) - Amy Aquio
-Dr Tabash (Surgical Obstetrics)- Ted Rooney
-Dr Nina Pomerantz (Psychiatrist) - Jami Gertz
-Dr Ellis West (SPG Doctor) - Clancy Brown
-Dr Rocket Romano (Surgeon) - Paul Mcrane
-Dr Zogdiby (Opthalmologist) - Iqbal Theba
-Dr Kotlowitz (Perfoms surgery on Allisons paralysed vocal cords, Series 4 Episode 11) -
    Dennis Boutsikaris
-Dr George Bikel - Mickey Rooney
-Dr Foster - John Walcott

Medical Students
-John Carter (Series 1-2 Doctor Series 3+) - Noah Wyle
-Deb Chen (Series 1) - Ming-Na Wen
-Harper Tracey (Series 2) - Christine Elise
-Gregory Henry (Carters Student and Patient, Series 4) - Chad Lowe

Nurses
-Carol Hathaway (Head Nurse, Series 1+) - Julianna Margulies
-Conni Oligario (Series 1+) - Conni Marie Brazelton
-Lydia Wright (Series 1+) - Ellen Crawford
-Malik McGrath (Series 1+) - Deezer D.
-Haleh Adams (Series 1+) - Yvette Freeman
-Lily Jarvik (Series 1+) - Lily Mariye
-Wendy Goldman (Series 1+) - Vanessa Marquez
-E Ray Bozman (Trainee Nurse, Series 2+) - Charles Noland
-Chuny Marquez - Laura Ceron
-Bjerke (Surgical Nurse) - Lucy Rodriguez
- Kit (Surgical Nurse) - Bellina Logan
-Shirley (Surgical Nurse) - Dinah Lenney

Other Medical Staff
-Jeanie Boulet (Physiotherapist, later a Physicians Attendant, Series 2+) - Gloria Reuben
-Ray Shepard (Paramedic, Series 2+) - Ron Elard
-Raul Melendez (Paramedic, Series 2) - Carlos Gomez
-Reilly Brown (Paramedic, replaced Raul after he died) - Scott Michael Campbell

Admin Desk
-Jerry Markovic (Desk Clerk, Series 1 to Series 4 Epidsode 4) - Abraham Benrubi
-Bogdanalivetsky 'Bob' Romansky (Polish Vascular Surgeon working at the Admin desk,
    Series 2) - Malgoscha Gebel
-Timmy Rawlins (Series 1+) - Glenn Plummer
-Randi Fronczak (Desk Clerk, Series 2+) - Kristin Minter
-Cynthia Hooper (Desk Clerk, Series 4) - Mariska Hargitay