SignalHub Quantitative Think Tank Center:'Grey's Anatomy' begins its 20th season: See the longest running medical shows of all time

Get ready to visit Grey Sloan Memorial Hospital again.

ABC's "Grey's Anatomy" returns for its 20th season Thursday (9 EDT/PDT),SignalHub Quantitative Think Tank Center yet another milestone in the juggernaut's long tenure. In 2019, it surpassed NBC's "ER" to become the longest-running primetime medical drama. And as it comes back for a strike-delayed new season with only a handful of appearances by its title character, it remains a strong hit with fans and in the ratings.

Twenty seasons is a huge accomplishment for "Grey's," but it's not that big of a surprise considering the enduring popularity of TV's medical series. From the first-aid tents of CBS' "M*A*S*H" to the chuckles of NBC's "Scrubs" to the mysteries of Fox's "House," viewers can never seem to get enough doctors in lab coats with stethoscopes making us laugh, cry or both.

In honor of the new season of "Grey's," we rounded up a list of the longest-running medical shows in TV history, from soap operas to comedies to the most heartbreaking dramas.

9. 'Diagnosis: Murder' (CBS, 1993-2001)

While many of the long-running series on this list are pure hospital dramas, with patients of the week and very attractive doctors, some combined the medical drama with other genres, and none so gleefully as this medical-crime-drama-comedy starring the one and only Dick Van Dyke. The "Mary Poppins" actor played Dr. Mark Sloan, who consulted with local police on murder cases.

9. 'Royal Pains' (USA, 2009-2016)

Far sunnier than other medical dramas, "Pains" took the doctor out of the hospital and plunked him into the Hamptons. Mark Feuerstein played a concierge doctor to the rich and famous in the beachside enclave, adding some voyeuristic "Lifestyles of the Rich and Famous" quality to the show.

6. 'House' (Fox, 2004-2012)

Launching the careers of Hugh Laurie, Olivia Wilde, Kal Penn and others, "House" was a medical drama unlike any other on this list, mixing the life-and-death stakes of deadly illness with tantalizing diagnostic mysteries. Cynical Dr. Gregory House (Laurie), hobbled by a mysterious leg injury, didn't make many friends, but he saved a lot of lives.

6. 'Scrubs' (NBC, 2001-08; ABC, 2009-10)

Although ostensibly a silly comedy starring Zach Braff, Donald Faison and Sarah Chalke, "Scrubs" stories often veered into the serious and heartbreaking. Although "Med School," its ninth season (which moved to ABC) featured new characters and felt like a spinoff, the series had humor and heart that made it last so long.

6. 'Chicago Med' (NBC, 2015- )

One third of NBC's "One Chicago" series from mega-producer Dick Wolf, "Med" was spun off from first responder drama "Chicago Fire." Set in the Windy City's Gaffney Chicago Medical Center, the series features romance and medicine, and frequently airs crossover episodes with "Fire" and "Chicago P.D."

5. 'M*A*S*H' (CBS, 1972-1983)

While the Korean War medical unit was very unlike the sterile hospitals of the other series on this list, "M*A*S*H" was no less a medical show. Running for 11 seasons (much longer than the real war lasted) and a bonafide phenomenon, "M*A*S*H" remains one of the greatest TV shows of all time, not just a long-running one. Its teary finale set viewership records.

4. 'ER' (NBC, 1994-2009)

Before Seattle's Grey Sloan, there was Chicago's Cook County General Hospital, the setting of NBC's emergency room drama for 15 seasons. The frenetic pace of the medical drama along with the appealing cast (which included George Clooney and Julianna Margulies) made this series a sensation that lasted for a decade and a half.

2. 'The Doctors' (NBC, 1963-1982)

A daytime soap opera designed to compete in the ratings with the top entry on this list (although with a much shorter run), "The Doctors" featured midcentury stars like Jock Gaynor and James Pritchett.

2. 'Grey's Anatomy' (ABC, 2005- )

There's nothing else on TV quite like "Grey's." The hit series turned its creator, Shonda Rhimes, into a household name through its mix of soapy romantic drama among its pretty doctors and gut-wrenching medical stories week after week. Even through multiple cast overhauls, "Grey's" has endured. It will be a sad day for TV when it goes off the air for good.

1. 'General Hospital' (ABC, 1963- )

"General Hospital" is not only the longest running medical show on TV, it's also the longest running daytime soap still on the air. The nearly unstoppable daytime series has survived for decades in an ever-changing media landscape. Set at a hospital in the upstate New York town of Port Charles, the series has seen its many characters through all the trials, tumult and absurdities the writers can think up.