Cast

 Starred:

Ed Flanders as Dr. Donald Westphall (seasons 1-6, recurring season 6)	William Daniels as Dr. Mark Craig (seasons 1-6)	Norman Lloyd as Dr. Daniel Auschlander (seasons 1-6, featured season 1)
David Birney as Dr. Ben Samuels (season 1)	Ronny Cox as Dr. John Gideon (season 6)
Also starred (in alphabetical order):
G.W. Bailey as Dr. Hugh Beale (season 1)	Bonnie Bartlett as Ellen Craig (seasons 1-6, starring seasons 5-6)	Ed Begley, Jr. as Dr. Victor Ehrlich (seasons 1-6)	Ellen Bry as Nurse Shirley Daniels (seasons 1-3, featured season 1)
Stephen Furst as Dr. Elliott Axelrod (seasons 2-6, featured season 2)	Bruce Greenwood as Dr. Seth Griffin (seasons 5-6)	Mark Harmon as Dr. Bobby Caldwell (seasons 2-4)	Terence Knox as Dr. Peter White (seasons 1-3)
Eric Laneuville as Luther Hawkins (seasons 1-6,  featured season 1)	Sagan Lewis as Dr. Jacqueline Wade (seasons 1-6, starring season 6)	Howie Mandel as Dr. Wayne Fiscus (seasons 1-6)	Kim Miyori as Dr. Wendy Armstrong (seasons 1-2, featured season 1)
David Morse as Dr. Jack Morrison (seasons 1-6)	France Nuyen as Dr. Paulette Kiem (seasons 5-6, starring season 6)	Christina Pickles as Nurse Helen Rosenthal (seasons 1-6)	Cindy Pickett as Dr. Carol Novino (seasons 4-6, featured season 4)
Kavi Raz as Dr. Vijay Kochar (seasons 1-6, recurring seasons 3-6)	Jennifer Savidge as Nurse Lucy Papandrao (seasons 1-6, starring season 6)	Cynthia Sikes as Dr. Annie Cavanero (seasons 1-3)	Nancy Stafford as Joan Halloran (seasons 2-4, recurring seasons 3-4)
Denzel Washington as Dr. Philip Chandler (seasons 1-6)
and featured:
Barbara Whinnery as Dr. Cathy Martin (seasons 1-3)	Alfre Woodard as Dr. Roxanne Turner (seasons 4-6, recurring seasons 5-6)

Recurring characters:

Hospital staff:

Paul Sand as Dr. Michael Ridley (season 2) Psychiatrist.

Byron Stewart as Warren Coolidge (seasons 3-6) Orderly.

Philip Sterling as Dr. Simon Weiss (seasons 2-6) Psychiatrist.

Frank Dent as Dr. Steven Kiley (seasons 1-6) Resident surgeon.

Jack Dodson as Judge Thornton Farnham (seasons 3-6) Hospital board member.

Edward Herrman as Father Joseph McCabe (seasons 4-5) Founder and Chief of Services at St. Eligius.

Al Ruscio as Rawly Moreland (seasons 2-3) Head of maintenance.

Reid Shelton as Dr. Isaac Barton (seasons 2-6) Urologist.

Arthur Taxier as Dr. Morton Chegley (seasons 1-2, 6) Oncologist.

Family & relationships:

Dana Short as Lizzie Westphall (seasons 1-6) Donald's daughter.

Chad Allen as Tommy Westphall (seasons 2-6) Donald's son.

Herb Edelman as Richard Clarendon (seasons 2-6) Helen Rosenthal's boyfriend.

Alan Oppenheimer as Ira Rosenthal (season 1) Helen's fourth husband.

Jeannie Elias as Marcy Eisenberg (seasons 2-6) Helen's daughter from her first marriage.

Ian Fried as Jeff Rosenthal (seasons 2-6) Helen's son from her fourth marriage.

Cady McClain as Erin Scheinfeld (seasons 2-3) (as Katie McClain) Helen's daughter from her second marriage.

Karen Petraszek as Julie Silverman (seasons 2-4) Helen's daughter from her third marriage.

Jonathan Chapin as Jimmy Silverman (seasons 2-4) Helen's son from her third marriage.

Karen Landry as Myra White (seasons 1-3) Peter's wife.

Candace Cameron as Megan White (seasons 1-3) Peter's daughter.

Deborah White as Nina Morrison (seasons 1-2) Jack's first wife.

Jean Bruce Scott as Roberta Sloan (season 2) Victor's first wife.

Helen Hunt as Clancy Williams (seasons 2-4) Jack's girlfriend.

Patricia Wettig as Joanne McFadden (seasons 5-6) Jack's second wife.

Jane Wyatt as Katherine Auschlander (seasons 2-6) Daniel's wife.

Geraldine Fitzgerald as Margaret Ryan (seasons 2, 5) Daniel's long lost love.

Tanya Berezin as Constance (seasons 4-6) Donald's sister-in-law.

Betty White as Captain Gloria Neal (seasons 3-4) Donald's friend from med school.

Scott Paulin as Steven Craig (seasons 1-4) Mark's son.

Louis Nye as Dr. Milton Axelrod (seasons 5-6) Elliott's father.

Bill Dana as Jonas Fiscus (seasons 5-6) Wayne's father.

Lainie Kazan as Frieda Fiscus (season 6) Wayne's mother.

Steve Allen as Lech Oseransky (seasons 5-6) Victor's father.

Jayne Meadows as Olga Oseransky (seasons 5-6) Victor's mother.

Louise Lasser as Aunt Charise (season 2) Victor's aunt.

Staff with story arcs:

Karen Austin as Dr. Mary Woodley (season 3) Head of E.R.

Jamie Rose as Dr. Susan Birch (season 5) First-year resident doctor.

Melinda Culea as Nurse Julie McPhail (season 5) Ward nurse.

Leah Ayres as Nurse Mona Polito (season 4) Surgical nurse, and Wayne's girlfriend.

Vivian Bonnell as Nurse Skilling (season 1) Ward nurse.

Melody Anderson as Nurse Jill Roberts (season 1) Ward nurse, and Peter's girlfriend.

Jane Kaczmarek as Nurse Sandy Burns (season 1) E.R. nurse, and Peter's girlfriend.

Stacey Dash as Penny (season 6) Video producer, and Luther's fiance.

Rosanne Katon as Amanda Taylor (season 2) (as Rosanne Katon Walden) Physiotherapist and Phil's girlfriend.

Dorothy Fielding as Dr. Nancy Paxton (season 1) Visiting doctor and former girlfriend of Dr. Samuels.

Caroline McWilliams as Dr. Christine Holtz (season 3) Visiting doctor and Annie's house guest.

Christopher Guest as B.J. Cummings (season 1) Hospital administrator.

Other recurring supporting staff:

Christina Kokubo as Paramedic Faith Yee (seasons 3-6) Paramedic.

S. Pearl Sharp as Nurse Peggy Shotwell (seasons 3-6) (as Saundra Sharp) Nurse.

Rae Dawn Chong as Billie Vaughan (seasons 2-3) Clerk.

John Corey as Tony Clifton (season 3) Telephone installer.

Rafael Campos as Ramon Lopez (season 1) Purchasing manager.

Roxanne Reese as Nurse Louise (season 1) Nurse.

Lance Guest as Sean Rooney (season 1) Orderly.

Gretchen Wyler as Joanne Jesmer (season 2) Member of the Women's Auxiliary.

Tom Henschel as Kyle (seasons 4, 6) Maintenance man.

Karl Lukas as Carl (seasons 4, 6) Maintenance man.

Recurring patients and featured characters:

Florence Halop as Florence Hufnagel (season 3) Recurring patient.

Todd Susman as Victor Bevine (seasons 4-6) Recurring patient and Dr. Westphall's moving man.

Oliver Clark as John Doe #6 (seasons 4-5) Recurring psychiatric patient with amnesia.

Jeff Allin as Alex Corey (seasons 3-6) Local artist.

Robert Costanzo as Mr. Broadwater (seasons 1, 4, 6) Bypass patient.

Patients and companions with story arcs:

Deborah May as Terri Valere (season 4) Fertility patient trying to conceive.

George DelHoyo as Ken Valere (season 4) (as George Deloy) Fertility patient whose wife is trying to conceive.

Marian Mercer as Eve Leighton (season 2) Heart transplant recipient.

Stephen Elliott as Manny Schecter (season 3) Firefighter and burn victim.

Ernie Hudson as Jerry Close (season 3) Firefighter and burn victim.

John Hammond as Michael Duffy (season 3) Firefighter and burn victim.

Richard Marcus as "Rockin'" Ralph Selover (season 1) Psychiatric patient.

Laraine Newman as Jane Sondell a.k.a. Tweety (season 1) Psychiatric patient.

Murray Rubin as Murray Robbin (season 3) Patient and friend of Mrs. Hufnagel.

Kyle Secor as Brett Johnston (season 6) AIDS patient.

John Scott Clough as Kevin O'Casey (seasons 4, 6) Son of a polio patient, grandson of a bypass patient, boyfriend of Brett Johnston.

Tim Robbins as Andrew Rhinehardt (season 1) Self-inflicted terrorist bombing victim.

Jack Bannon as Stephen McAllister (seasons 1, 4) Husband of bombing victim.

Tom Hulce as John Doe #12, a.k.a. David Stewart (season 1) Shooting victim and amnesiac.

Eric Stoltz as Eddie Carson (season 2) Assault victim.

Dan Hedaya as Joseph Keuhnelian (season 2) Epilepsy patient.

Lycia Naff as Maddy (season 3) Pregnant fourteen-year-old girl.

Timothy Van Patten as Dean (season 3) Father of Maddy's child.

Ann Hearn as Andrea Fordham (season 3) Facial fibromatosis patient.

Piper Laurie as Fran Singleton (season 2) Stroke victim.

Alan Arkin as Jerry Singleton (season 2) Fran Singleton's husband.

John Schuck as Andy Wegener (season 3) Jack Morrison's neighbour; undergoes dangerous procedure when his daughter suffers liver damage.

Brandy Gold as Alexis Wegener (season 3) Liver damage patient.

Mimi Kennedy as Lois Wegener (season 3) Alexis Wegener's mother and Andy's ex-wife.

Amanda Wyss as Pru Dowler (season 4) Mentally challenged abortion patient.

Dorothy McGuire as Augusta Endicott (season 4) Bypass patient and matriarch of a prominent political family.

Charles Cioffi as Senator Gordon Endicott (season 4) Augusta Endicott's son.

Kathy Bates as Polly (season 5) Homeless person with Tourette's syndrome.

David Wayne as Dr. George Wyler (season 3) Dr. Auschlander's friend, searching for a kidney for a young African.

Larry B. Scott as Tshalla (season 3) Young African kidney transplant patient.

Michael Learned as Sister Millicent Domenica (season 3) Mother superior who refuses life support for a comatose nun.

Beatrice Straight as Marjorie Andrews (season 6) Rehab patient.

David Ackroyd as Col. Chuck Cochrane (season 4) Astronaut with Guillain–Barré syndrome.

John Kellogg as Henry Spooner (season 6) Artificial heart patient.

Neva Patterson as Marguerite Spooner (season 6) Wife of artificial heart patient.

Harold Gould as Melvin Millstein (season 3) Bone marrow recipient.

Bill Macy as Hershel Millstein (season 3) Bone marrow donor.

Other recurring supporting characters:

Suzanne Lederer as Yvonne Galecki (seasons 3-5) Steven Craig's wife.

Ramon Bieri as Gene Galecki (season 4) Steven Craig's father-in-law.

K Callan as Patty Galecki (season 4) Steven Craig's mother-in-law.

Michael Richards as Bill Wolf (seasons 2-3) TV producer.

Casey Siemaszko as Rick Messina (seasons 3-4) Lizzie Westphall's boyfriend.

John Dennis Johnston as Nick Moats (seasons 4-5) Convict, rapist and hostage-taker.

Austin Pendleton as Mr. Entertainment (season 2) Janitor and compulsive entertainer.

Gerald Hiken as Robin Baskins (season 5) Mark and Ellen's friend from college.

This list is by no means complete, nor does it reflect the frequency with which a character appeared, but rather represents the selection of actors/characters I remember most, cherrypicked from IMDB's "Full Cast and Crew" page for the show.