The fourth season of the American fictional drama television series ER first aired on September 25, 1997, and concluded on May 14, 1998.

After a surgical accident takes a man's life, Morgenstern decides to permanently step down as head of the ER and he leaves the hospital.

Corday came to America under the fellowship of Dr. Robert "Rocket" Romano (played by Paul McCrane), but their relationship sours towards the end of the season.

While there, Greene visits his own parents, where he finds out that his mother is sick, and his relationship with his dad continues to be strained.

Back in Chicago, he begins to date new ER desk clerk Cynthia Hooper (played by Mariska Hargitay).

After the awkward breakup, Cynthia leaves, but Greene stays to take care of his ailing mother and begin to mend his relationship with his father.

She begins to date a Synergix representative, Ellis West, who advises her to fire a physician's assistant, which happens to be Jeanie Boulet.

Carter pretends to be of humble origins in order to impress Anna, which fails when she finds out he actually comes from a wealthy family.

Paul Manning left his supervising producer role but remained involved with the series as an executive consultant.

Long-time crew members Lance Gentile and Neal Baer were promoted to producers for the fourth season.

Following his departure Adams was promoted to producer and Richard Thorpe and Michael Salamunovich joined the production team as co-producers.

Salamunovich was the series unit production manager for the first three seasons and continued to fulfill this role as a co-producer.

Third season regular writer Samantha Howard Corbin became a story editor and wrote three more episodes.

Other directors making their series debut with the fourth season were executive producer John Wells, Christopher Misiano, T.R.

Regular directors returning to the series for single episodes include Jonathan Kaplan, Félix Enríquez Alcalá, Lesli Linka Glatter, and Thomas Schlamme.

Editor Jacque Toberen and producer Lance Gentile each directed a single episode of the fourth season.

NOTE 1: First appearance of Dr. Elizabeth Corday Hathaway comes up with the idea of a pediatric clinic for the ER, and starts looking for funding.

Corday works to save a man trapped deep inside a collapsed building at a chemical plant.

A chemical spill at the plant sends the ER into chaos; Weaver collapses from the fumes and Carter has to take charge.

As the ER is evacuated, Ross and Hathaway take risks to save a sick girl and get stuck in an elevator when a fire alarm shuts them down.

As Josh, the methadone-addicted baby, recovers from an ultra-rapid detox, Ross' personal and professional relationships suffer.