- Doctors and Medical students
- Sam Anderson as Dr. Jack Kayson – Chief of Cardiology
- Amy Aquino as Dr. Janet Coburn – Chief of Obstetrics and Gynecology
- John Aylward as Dr. Donald Anspaugh – Surgical Attending Physician and Hospital Board Member
- Elizabeth Mitchell as Dr. Kim Legaspi – Psychiatrist
- David Brisbin as Dr. Alexander Babcock – Anesthesiologist
- John Doman as Dr. Carl DeRaad – Chief of Psychiatry
- Megan Cole as Dr. Alice Upton – Pathologist
- Christopher John Fields as Dr. Phil Tobiason
- Iqbal Theba as Dr. Zagerby – Ophthalmologist
- Nurses
- Ellen Crawford as Nurse Lydia Wright
- Conni Marie Brazelton as Nurse Conni Oligario
- Deezer D as Nurse Malik McGrath
- Laura Cerón as Nurse Chuny Marquez
- Yvette Freeman as Nurse Manager Haleh Adams
- Lily Mariye as Nurse Lily Jarvik
- Gedde Watanabe as Nurse Yosh Takata
- Dinah Lenney as Nurse Shirley
- Kyle Richards as Nurse Dori Kerns
- Lucy Rodriguez as Nurse Bjerke
- Morris Chestnut as ICU Nurse Frank 'Rambo' Bacon
- Elizabeth Rodriguez as Nurse Sandra
- Mary Heiss as Nurse Mary
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- Staff, Paramedics and Officers
- Troy Evans as Desk Clerk Frank Martin
- Kristin Minter as Desk Clerk Miranda "Randi" Fronczak
- Pamela Sinha as Desk Clerk Amira
- Erica Gimpel as Social Worker Adele Newman
- Skip Stellrecht as Chaplain Miller
- Emily Wagner as Paramedic Doris Pickman
- Montae Russell as Paramedic Dwight Zadro
- Lynn A. Henderson as Paramedic Pamela Olbes
- Demetrius Navarro as Paramedic Morales
- Brian Lester as Paramedic Brian Dumar
- Michelle Bonilla as Paramedic Christine Harms
- Claudine Claudio as Paramedic Silva
- Meg Thalken as Chopper EMT Dee McManus
- Ed Lauter as Fire Captain Dannaker
- Chad McKnight as Officer Wilson
- David Roberson as Officer Durcy
- Joe Basile as Officer Tom Bennini
- Family
- Frances Sternhagen as Millicent Carter
- Jonathan Scarfe as Chase Carter
- George Plimpton as Grandpa Carter
- Sally Field as Maggie Wyczenski
- Mark Valley as Richard Lockhart
- Nancy Kwan as Mrs. Chen
- Christine Harnos as Jennifer Simon
- Khandi Alexander as Jackie Robbins
- Andrew McFarlane as Jesse Robbins
- Lisa Nicole Carson as Carla Simmons
- Victor Williams as Roger McGrath
- Matthew Watkins as Reese Benton
- Paul Freeman as Dr. Charles Corday
- Judy Parfitt as Isabelle Corday
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