Though Law & Order: Special Victims Unit has surpassed its predecessor's longevity, the original Law & Order still ranks as one of the longest-running primetime series in American television history; the police procedural aired new episodes on NBC across the span of two decades (via NBC). 

Of course, with any TV show that runs that long, you're bound to see some turnover, and Law & Order cycled through dozens of series regulars over its 20-season run. In fact, by the time the show ended in 2010, not a single original cast member was left. (The longest-serving actor at the time was S. Epatha Merkerson, who started playing Lieutenant Anita Van Buren in season 4.)

Many of the Law & Order stars left the show simply because they were ready for new projects, while other actors left because of behind-the-scenes issues. To quote the Law & Order intro voiceover, these are their stories...

George Dzundza realized Law & Order wasn't for him

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The first actor to leave Law & Order was George Dzundza, who made his exit in 1991 after just one season of playing Sergeant Max Greevey, the seasoned detective partner of Chris Noth's Mike Logan. "I felt that it was a plot-driven show," Dzundza told PopEntertainment in 2003, reflecting on saying yes to the series. "There was a lot of interplay between Chris and I."

As season 1 progressed, however, Dzundza found the stories to becoming "more Dragnet-like... I said no, this is not for me," he continued. "This is not what I signed on to do. And I had to take care of my family, frankly, as well." And so, in the season 2 premiere, Greevey — played by a body double — is gunned down outside his home.

Dzundza went on to star in the first seasons of two other series: the NBC  Jesse and the CBS crime drama Hack. And between 2005 and 2007, he had a memorable arc on Grey's Anatomy, playing the ailing father of George O'Malley (T.R. Knight).

Law & Order's Paul Sorvino wanted to pursue a singing career

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The actor behind Sergeant Phil Carreta, Mike Logan's partner after Max Greevey's death, lasted little more than one season on Law & Order. Paul Sorvino left in 1992, midway through season 2, with his character getting shot in the line of duty and transferred to a desk job.

The Orlando Sentinel reported at the time that Sorvino exited the role because he wanted to pursue a singing career. And sure enough, nearly a decade and a half later, the actor starred in the New York City Opera's 2006 production of The Most Happy Fella. "The part is close to two octaves here and there," he told TheaterMania at the time. "In my voice, I have three octaves. I don't find the range daunting, but to do it right is daunting. I want to do it right."

More recently, Sorvino guest-starred in episodes of Elementary, The Goldbergs, and Grandfathered. And in 2019, he started starring in the Epix crime drama Godfather of Harlem, playing real-life crime boss Frank Costello.

Law & Order's Michael Moriarty had issues with then-Attorney General Janet Reno

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After four seasons of playing Executive Assistant District Attorney Ben Stone on Law & Order, Michael Moriarty departed 1994 amid a public conflict with then-Attorney General Janet Reno; at the time, she'd endorsed legislation to limit violent programming like Law & Order.

After meeting with Reno — alongside producer Dick Wolf and other NBC bigwigs — Moriarty criticized her in a news conference, according to the Los Angeles Times. But no one rallied to his side, and Moriarty ended up leaving Law & Order, claiming the writers punished him for his activism. (On the show, Stone resigns from his post after a witness whose testimony he coerced is murdered.)

Moriarty told The Wall Street Journal in 2000 he left Law & Order because of "creeping McCarthyism," saying Reno's crusade against TV violence amounted to censorship. He continued acting, however, appearing in the films Courage Under Fire and Shiloh, and the TV shows Touched by an Angel and The 4400. Moriarty also won a 2002 Emmy Award for his performance as Winston Dean in the TV movie James Dean.

Chris Noth from Law & Order was ready for a film career

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Detective Mike Logan continued crime-solving until the end of Law & Order's fifth season in 1995, when actor Chris Noth took his leave of the program. According to the Associated Press, producer Dick Wolf said Noth was due for a "huge" raise that would be "impossible to grant."

However, the head of the Noth's management company said the actor was ready for a film career anyway. "He's really sorry that they couldn't get it together, but he's had five great years, and his feeling is that it's time to move on," they shared. Logan exits the Law & Order plot when he punches a politician and gets transferred to a job in Staten Island, though Noth later reprised the part in the TV movie Law & Order: Exile and the spinoff Law & Order: Criminal Intent.

Noth didn't rest on his laurels after leaving Law & Order, though he's known more for his TV roles than his film work. He played love interest Mr. Big on the HBO rom-com Sex and the City, for example, and philandering husband Peter Florrick on the CBS legal drama The Good Wife.

Dann Florek and Richard Brooks were let go from Law & Order to make room for female characters

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For the first three seasons of Law & Order, Dann Florek played Captain Donald Cragen and Richard Brooks played Assistant District Attorney Paul Robinette. When season 4 picked up in 1993, however, both characters were gone without explanation. According to a 1997 Orlando Sentinel report, both actors were let go from Law & Order to open up cast positions for the series' two lead female characters: Lieutenant Anita Van Buren and Assistant District Attorney Claire Kincaid. 

Both Florek and Brooks eventually returned as guest stars in subsequent seasons of Law & Order. Additionally, Florek starred in the first 15 seasons of Law & Order: Special Victims Unit; he left the spinoff show in 2013 because his character reached the mandatory NYPD retirement age, as showrunner Warren Leight explained at the time (via E! News). Brooks, meanwhile, moved on to other TV projects, including a starring role on Being Mary Jane and recurring parts on The Flash, All Rise, Bosch, The Haves and the Have Nots, and Good Trouble.

Jill Hennessy found her Law & Order role limited

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Jill Hennessy played Assistant District Attorney Claire Kincaid from season 4 to season 6 of Law & Order, leaving the show in 1996. In the plot, Kincaid dies in a car accident as she drives a drunk Lennie Briscoe home from a bar.

In a 2006 interview with The Morning Call, Hennessy said the role of an ADA on Law & Order is "limited" since the characters are supposed to keep their personal feelings out of the job. "One of the reasons you see actors moving on is that it's so easy to become typecast," she explained. "If they see you in that one light, people presume that's all you can do. I was getting that from day one, with casting directors basically thinking, 'She can't do comedy. She can't do emotional work.'" Hennessy added that actors usually strive for variety in their career, as opposed to staying in one genre.

Hennessy later led the cast of the NBC procedural Crossing Jordan before taking parts in the TV shows Madam Secretary and Shots Fired. In 2019, she started starring as Jenny Rohr in the Showtime drama City on a Hill.

Benjamin Bratt left Law & Order to spend time with his family

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Mike Logan's replacement was Detective Rey Curtis, who entered the Law & Order universe in season 6 and exited at the end of season 9 in 1999. In that season's finale, Curtis takes an early retirement to tend to help his wife manage her MS.

And offscreen, actor Benjamin Bratt had family on his mind, too. "After four years I've felt like it was time to get back home to my family," Bratt said in a statement, per the New York Post. "How do you walk away from the best job in the world, and a group of people you've grown to love?" Bratt added that it was an "extremely difficult decision," but expressed hope that he'd be able to work with his Law & Order colleagues again. And sure enough, he came back to the show for one episode in season 20.

After leaving the show, Bratt went on to appear in the films Miss Congeniality, Traffic, and Coco, and starred in the TV shows The Cleaner, Private Practice, 24: Live Another Day, and Star.

Steven Hill reportedly couldn't keep up with the Law & Order filming schedule

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Steven Hill, who was already famous for the TV series Mission: Impossible by the time he landed his Law & Order part, played District Attorney Adam Schiff on the NBC show. He bid his castmates goodbye in 2000, with his character leaving his job at the end of season 10 to coordinate commemorations of the Holocaust Project. Producer Dick Wolf later told Newsday that Hill, then 78, left the show because he was tired and didn't want to commute from the suburbs into Manhattan every week.

Law & Order ended up being Hill's final onscreen acting role; the actor died in 2016 at the age of 94. "Steven was not only one of the truly great actors of his generation, he was one of the most intelligent people I have ever met," Wolf told Variety at the time, eulogizing the late TV star. "He is also the only actor I've known who consistently tried to cut his own lines. He will be missed, but fortunately, he can be seen ubiquitously on Law & Order reruns."

Law & Order's Angie Harmon wanted to follow her big-screen dreams

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From season 9 to season 11 of Law & Order, Angie Harmon portrayed Assistant District Attorney Abbie Carmichael. She gave up the role in 2001 for a variety of reasons, as she told Cinema Confidential two years later: the show took her away from her then-husband, for example, and her role was feeling one-note.

But most of all, Harmon had her sights on the silver screen. "I left Law & Order because I really honestly did want to do movies and did want to be a movie star since I was a little girl," she revealed. "I loved the show. It just kind of got to the point where... the character can't grow and do anything else."

Harmon did star in a handful of films, including Agent Cody Banks and Fun With Dick and Jane. But before long, she ended up back on television, starring in the NBC medical drama Inconceivable and the ABC procedural Women's Murder Club. Harmon is probably best known, however, for her long-running role as Jane Rizzoli on the TNT procedural Rizzoli & Isles.

Jerry Orbach moved to another Law & Order show amid a cancer battle

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Jerry Orbach — then famous for his Broadway turns in the musicals Guys and Dolls, Chicago, and 42nd Street – joined Law & Order in season 3 to replace Paul Sorvino. Orbach played Detective Lennie Briscoe, staying on the show until 2004, when the character retired at the end of the 14th season. That retirement was short-lived, however; Orbach reprised the part in the first two episodes of the short-lived spinoff show Law & Order: Trial by Jury.

Before his Law & Order exit, Orbach told his colleagues he was battling prostate cancer, and it was that disease that led to his death at age 69 later that year, according to the Los Angeles Times. Producer Dick Wolf paid tribute to the veteran actor in a statement to the Times. "I'm immensely saddened by the passing of not only a friend and colleague, but a legendary figure of 20th century show business who was a star of screen, stage, and television," he shared. "He was one of the most honored performers of his generation. His loss is irreplaceable."

Elisabeth Röhm felt like she couldn't offer her Law & Order character anything else

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Elisabeth Röhm joined Law & Order at the start of season 12, and left three seasons later, bidding farewell to the role of Assistant District Attorney Serena Southerlyn in 2005. In the show, District Attorney Arthur Branch fires Southerlyn for being too emotional; then, in one of the more controversial Law & Order moments, she comes out as gay during the firing. According to the Chicago Tribune, GLAAD criticized the last-minute reveal, saying it was "really disappointing to have one of the leads come out five seconds before she exits the show."

Talking to Today at the time, Röhm explained that she felt finished with the role. "I traveled and I shot a film this summer, and it opened my eyes to something beyond what's comfortable, and I realized that I didn't have anything else that I could offer this character," she revealed. Röhm's roles in the years since include parts in the films American Hustle, Joy, and Bombshell and in the TV shows The Last Ship, The Oath, and Jane the Virgin.