When Ken Levine and David Isaacs were writing scripts for the TV series M*A*S*H, they had no idea that nearly 30 years later they'd still be watching and discussing the episodes.

But here they are - on the line from Los Angeles - recalling their work on one of the best-loved, highest-rated, taboo-breaking series of all time.

For 11 years, M*A*S*H was on top, winning not only high ratings but 99 Emmy nominations and 14 awards as subjects including adultery, racism, homosexuality and violence were tackled.

The series was spun off from the feature film starring Elliott Gould and Donald Sutherland as surgeons operating in a Mobile Army Surgical Hospital during the Korean War. The movie, based on a novel by a doctor who served in a real M*A*S*H unit, was nominated for a best picture Oscar and won one for best screenplay.

The success prompted 20th Century Fox Television and CBS to develop the idea into a TV comedy series, produced by Gene Reynolds.

Alan Alda was recruited to play the small screen Hawkeye, with Wayne Rogers as Trapper John and Loretta Swit as Hot Lips Houlihan. Over the years there were changes in the cast. Harry Morgan came in as Colonel Sherman Potter. Mike Farrell's Captain B J Hunnicut took Trapper's place in the operating theatre and Hawkeye's life.

By the eleventh season, although the series was still high in the ratings, the creative team were feeling the pressure of finding new ideas. They voted to bring the show to a conclusion, with M*A*S*H airing for the last time on US TV screens in February 1993. After 251 episodes, the series ended with the final episode that attracted one of the highest ever TV audiences.

Levine and Isaacs wrote episodes together during the latter half of the 1970s, including the sixth season which is available on DVD this month.

"It's strange talking about the show because so much has been written about it and there's been so much analysis. At the time, we were just trying to get the outline done and go to lunch," says Levine. "I'm just glad that we weren't thinking, 'what are they going to be writing in 30 years time'."

Sometimes Isaacs revisits episodes on DVD. "When I watch them it really takes me back to when we were doing them. And I'm forever going, 'we should have done that or this a little better'," he says.

Neither had an inkling the series would be available to watch at home three decades later. DVD wasn't around in 1976. "It was three-quarter inch video back then," he says.

Although the pair have gone on to write for other hit US comedies, including Cheers and Frasier, M*A*S*H has a special place because it was the first series for which they wrote.

They met in the army, where they served in the same unit, and decided they wanted to become writers. Their familiarity with the military and army thinking was a bonus for writing for M*A*S*H. "That was a dream and it became a dream come true," says Levine.

"It was our first assignment. We'd sold a couple of other shows and then our agent moved to the same agency as Gene Reynolds, who produced the show. We were invited to go in and pitch story ideas."

Reynolds liked what he heard and they were taken on, writing 17 episodes between 1976 and 1979. Just as the book and film were based on real life, so was the TV series. They had access to interviews with real M*A*S*H doctors which provided the inspiration for stories for Hawkeye and the rest of the characters.

"In those days the writing staffs were much smaller," says Isaacs. "There were only about five of us writing on the show at any given time. Ken and I always wrote together."

The series was already a success when they joined. "I was aware that the show had a big following and had made a huge impact," says Levine. "We would see something on air and hear friends and various people talking about it the next day. I remember saying to David Ogden Spiers the night of his first episode that his life would be completely changed."

Isaacs points to the way the series consumed material. With two or three stories each episode, by the end of the seventh season he and Levine decided they'd gone as far as they could. "We pretty much felt we'd done every show - a hot show, a cold show, visiting general, mysterious disease and Klinger had worn every kind of dress," he says.

"The characters were just not surprising any more. But we continued to watch. You feel part of it. It's a real fraternity. I know this is an American analogy but a couple of years ago we had a M*A*S*H reunion with all these actors and writers and I felt like I was part of a Superbowl winning team."

The series stood out as different from other US comedy shows. "Part was the time in which it was done," says Isaacs. "The Vietnam War was going on and there was a great element of association with the show. I think the general humanity was the deciding factor and the fantastic actors. At the centre was a tremendous real sense of absurdity more than the average sit-com. In a way, it's unique in US sitcoms."

* The sixth season of M*A*S*H is released to buy on DVD from Twentieth Century Fox Home Entertainment on March 28, price £22.99.