The pilot for the popular TV series is set during 24 frantic hours in the lives of a group of doctors, nurses, and staff members of a busy emergency room at a Chicago hospital. They deal with the seemingly endless casualties that stumble into their place of employment. The central characters are the chief resident and family man Dr. Mark Greene, who is considering a job in private practice due to pressure from his demanding law student wife Jennifer; outgoing Dr. Doug Ross, who deals with cases in his own personal way; straight-arrow Dr. Susan Lewis, trying to get by another long 36-hour shift; inexperienced third-year med student John Carter; cocky surgical resident Dr. Peter Benton; and troubled chief nurse Carol Hathaway.

Mark's wife arrives in the ER with the news that she has passed her bar exams but several members of the staff interrupt their intimate celebration. Greene treats an elderly woman whose husband isn't ready to let her go. It's been eight weeks since Hathaway's attempted suicide, but Doug Ross has yet to bring himself to visit the woman he went out with for two years. Susan Lewis saves a newborn who is brought into the ER choking. She also argues with the psychiatric attending who refuses to admit a patient suffering from dementia. Carter finds himself having to care for a group of German tourists who are suffering from food poisoning. He also treats a young flirt with a rash. Benton treats a recent surgery patient and finds his correct diagnosis overturned by the man's physician. Susan Lewis treats a family struck by a drunk driver. The husband and daughter will survive but there is little hope for the woman. The drunk driver is also brought in suffering from only a few scratches.

Mark Greene's wife Jen gets a position clerking with a Federal judge. Unfortunately, it's in Milwaukee, 2 hours away and she wants Mark to look for a job there. Greene and Susan Lewis treat Samuel Gasner, a man who has been waiting for a heart transplant and who will not survive the night unless a donor can be found. John Carter is worried that his latest paramour may have left him with a souvenir of their sexual encounter. Doug Ross treats a young girl suffering from severe asthma but whose mother can't afford her medication. Benton treats Ivan the liquor store owner who is shot for the third time in as many weeks.

Doug Ross' hopes of renewing his relationship with Carol Hathaway take a positive turn after the two of them kiss following a particularly stressful trauma, but his hopes are dashed when she decides to move in with boyfriend Tag. John Carter has a particularly good day when Dr. Green successfully walks him through a complex procedure. Haleh takes Dr. Benton to task when he refuses to act as a role model for a young gangbanger she has an interest in. Benton is also competing with Dr. Langworthy for a prestigious fellowship. It's Susan Lewis' birthday and her sister Chloe shows up at the ER drunk.

Susan Lewis' boyfriend Div Cvetic, a psychiatric resident at County General, seems to be under a great deal of stress regularly lashing out at everyone. Doug Ross takes over for Mark Greene who takes a day off to be with his wife. He has a hard time keeping up with all the paperwork. John Carter is increasingly frustrated with Peter Benton who never seems to invite him to participate in surgeries. Benton learns the result of the fellowship he applied for and his mother shows up in the ER with a sprained ankle. Carol Hathaway treats a patient who was raped. A new ER aide, Bob, start work.

Carol Hathaway faces an ethical dilemma when a patient admits that he, and not his friend, was driving the car that ran a red light and killed a pedestrian. She decides to tell Tag about kissing Doug Ross. It's Thanksgiving and the doctors treat an animal rights activist who was attacked by the turkey he was trying to save. Doug Ross is going to the Bahamas with Linda Farrell and he is very much feeling like a kept man. Carter has to treat a transgender woman who has now reached an age where she can no longer pass as a woman. Carter's indifference is the final straw. Susan Lewis continues to worry about Div Cvetic, whose condition seems to be worsening.

Dr. Greene gets offered a new job by Morgenstern.

It's a day of birthdays. Peter Benton's mother is celebrating a birthday and he tries desperately to find someone to cover his shift. He makes a choice however when Dr. Hicks suggests that he's been absent too often and may wish to consider a leave of absence until his mother's situation is resolved. Carter thinks it's Benton birthday and has a surprise for him. Mark Greene's daughter is also having a birthday but he misses that due to an emergency at the hospital. An elderly, solitary man in the final stages of cancer arrives in the ER on his birthday. Carol Hathaway suggests to her fiancé that they adopt little Tatiana, the AIDS patient abandoned in the ER. Ross has to deal with a young child who was kicked out of a window.

Carol Hathaway goes ahead with her plans to adopt Tatiana, but her past history makes her ineligible. Benton continues to trade shifts so he can spend time with his mother but it all catches up with him and he has a run-in with Dr. Hicks. Doug Ross treats an abused child. Green, Benton and Carter take extraordinary measures to save a man they later learned had signed a DNR. A consultant arrives to study procedures in the ER, but all is not quite what it seems. Mark Green's wife Jen has an important announcement. Benton's mother has a serious accident when he falls asleep on the couch.

Dr. Greene is still haunted by the death of Jodi O'Brien and isn't sure he can function as a doctor. At Susan's urging, he takes the night off but unfortunately for him, the new head of the ER Dr. 'Wild Willy' Swift arrives unannounced. Susan impresses Swift with her handling of many cases on a busy night. She also has to deal with the case of a young man who has had the hiccups for two days but may in fact be suffering from something far more serious. Nurse Hathaway and fiancée Tag are still working out the details of their wedding. Peter Benton's mother is still hospitalized and he will not accept that her age and her injuries mean that she will need permanent nursing care. Dr. Ross is now dating Diane Leeds. John Carter and Deb Chen's attempts at oneupmanship is starting to take on ridiculous proportions.

Greene finds his marriage falling apart and is concerned at how little time he's spending with his daughter. He also treats an eight week old child with a heart murmur who requires surgery. Susan tries to get her pregnant sister Chloe to take her pregnancy seriously, but her head isn't quite into it. Benton tries desperately to find a surgeon who will operate on a 16 year-old with a severe brain aneurysm that could burst at any time. He's also concerned at his mother's care and is growing ever more attracted to Jeanie Boulet. Doug Ross' commitment to Diane Leeds gets more serious when he agrees to be an assistant coach for her son's little league baseball team.

Doug Ross and Nurse Hathaway treat a girls' basketball team from a local catholic school for meningitis. Their teachers also need to be tested but one of them confides in Hathaway that she may have a particular problem. Green and the Chief of Staff have a disagreement in the middle of a procedure. With the wedding only two weeks away, Tag and Carol Hathaway have to deal with all of the final preparations, not the least of which is writing their own marriage vows. Susan deals with a suicide victim who is using emotional blackmail to keep his girlfriend from leaving him. Susan reaches the breaking point with her sister Chloe and tells her she has to move out.

On a fateful Mother's Day, several staffers in the ER face possible life-changing events. Susan Lewis' sister Chloe gives birth to a beautiful - and healthy - baby girl. Things start to go wrong however when their mother Cookie - who had agreed to take in Chloe and the baby - suddenly decides she's done enough and Susan will have to take care of it. Carter turns down an offer for an ER sub-internship in the hopes that he'll get an offer in surgery. Dr. Hicks has news for him however. Benton's mother takes a turn for the worse. Carol Hathaway is overwhelmed with the final preparations as her wedding day approaches.

It's Carter's last day in the ER and finally fed up with Dr. Benton's apparent indifference, rejoices when he learns that he gets to write an appraisal on him. He subsequently regrets his negative input when he gets offered the surgical sub-internship he'd hoped for and learns that Benton gave him a glowing appraisal. He also spends a good part of the day with young leukemia victim who is fed up with life. Benton and Jeanie Boulet's relationship reaches a crossroads. Mark Greene is offered an attending position at the hospital but also learns that he is being sued for malpractice over his handling of the Jodi O'Brien case. The big day for Carol Hathaway and Tag is here but doubts creep in and one of them gets left standing at the altar.

Carter gets his first official patient while Doug treats a four-year-old Asian boy who has AIDS.

Jennifer and Rachel have been involved in a car accident and Mark rushes to Milwaukee where they're in the hospital.

Benton has to attend a banquet at Vucelich's home and asks Jeanie to go with him. Mark hesitates to tell Rachel about the divorce.

In order to avoid having to deal with her personal problems regarding little Susie, Susan wholly absorbs herself in her work.

Mark Greene strikes a deal with Kerry Weaver - he will support her application for an ER attending position if she in turn will support Susan Lewis for Chief Resident. When Susan doesn't get the job, Mark is told to go ask her why. Carter is finally going to graduate and wants Benton to attend the party his family is throwing for him. Unfortunately, Carter decides to sit with a young patient awaiting a liver transplant and misses his own graduation ceremony. With the news she has received about her former husband Al's health, Jeanie Boulet decides to have herself tested. Doug Ross' girlfriend Karen forges his prescription for percodan. Hathaway's boyfriend, Shep, is refusing to undergo his anger management treatment. Mark's ex-wife Jen tells him that she is going to re-marry. Loretta Sweet asks Greene if he would become guardian to her kids.

Mark and Kerry have to create a policy regarding HIV-positive employees, which leads to gossip amongst the nurses.

Race relations become an issue in the ER when Mark Greene treats two injured teenagers, one black and the other white, and assumes the black kid was a drug dealer. It turns the white kid was the drug dealer and the black kid is a high school basketball star and an innocent bystander. When the black student's older brother confronts him, he begins to question his own impartiality. Carol Hathaway helps a young woman who was drugged with Rohipnol and raped. Benton gets an interesting offer from Dr. Hicks. He also learns that Carla Reece has been admitted to the hospital. Dr. Carter treats a woman with a serious condition but he seems to be the only one who sees it. Mark Greene's daughter ends up spending the day in the ER when her mom has to rush to Florida to deal with a family emergency.

His ex-wife Jennifer tells Mark he can't see Rachel until he's got his act together. Reece gets to go home. Al has lost his job.

Jeanie believes she's been fired because she has HIV and fights her dismissal.

It's Halloween in the ER, and the medical students throw a party; as a result, Carter decides that Lucy isn't mature enough to take responsibilities. A candidate for the ER Chief position arrives from New York and drives home disappointment for Kerry. Mark screws up when he doesn't recognize a homeless schizophrenic woman is pregnant before treating her. Benton treats Corday to a fun Halloween.

Mark Green is in New York on New Years eve for cancer surgery. Meanwhile a father and son are involved in a car crash.

Greene's daughter comes to live with him and Corday. Carter and Abby become more intimate. Chen must prove her skills while saving a baby. Weaver terminates Malucci after witnessing him having sex in an ambulance.

As Dr. Greene's brain tumor begins affecting his coordination, he becomes concerned that his fate will be similar to the terminally ill patients he treats.

Dr. Greene's final days are spent in Hawaii with Rachel, teaching her to drive and surf. When he suffers a seizure, Elizabeth is called. Mark refuses to go home. He manages to make amends with his daughter before his eventual death.