Steven Bochco, who lit up the prime-time skies five years ago with "Hill Street Blues," is about to do it again. And most TV producers never even do it once. "Hill Street Blues" was a daring departure in episodic TV drama; Bochco's new show, "L.A. Law," is a daring departure from "Hill Street Blues."

Unquestionably the most talked about program on any network's fall schedule, "L.A. Law" upgrades and reinvigorates the lawyer show in the way "Hill Street" rewrote the book on TV cops. A two-hour pilot, which will air in September or early October, is the talk of the TV business right now. Some who've seen it call it the best film ever made for television.

The pilot had the unusual honor of a special screening, for a paying audience, at New York's Museum of Broadcasting. NBC will make it the first fall show it screens at the semiannual press tour for TV writers in Los Angeles later this month. Based on an advance look, it is safe to say the assembled critics will go ga-ga when they get a gander.

"L.A. Law" is Serious Television, a gripping ensemble drama with the kind of dark comic overtones one expects from Bochco. In one of the first scenes, a senior partner of the prestigious law firm where the series is set is found dead at his post, face first in a plate of pasta. As his corpse, frozen to its desk chair, is carried from the suite, one of the junior partners says sentimentally, "I've got dibs on his office."

Beautifully cast and acted -- including nine regular central characters and such guest litigants, in the pilot, as the stunning Alfre Woodard -- "L.A. Law" works because the lawyers come alive as vital characters, and the cases they take on are reflections of this fractious, disputatious modern world. You learn something about the law. You appreciate something about human nature.

Bochco, 42, one of the gray-haired golden boys of television, created the series with Terry Louise Fisher, an alumnus of "Cagney and Lacey" and a former lawyer herself. On a summery L.A. day, Bochco sits in his quiet, out-of-the-way office in the Old Writers' Building at 20th Century-Fox, a picture of anxious calm in television's panicky Pacific. Production on regular episodes of "L.A. Law," of which NBC has ordered 13, doesn't begin until July, but that doesn't preclude the occasional crisis. At the moment, secretaries are rushing to and fro trying to get "Law" producer Gregory Hoblit, another "Hill Street" veteran, on the line from Cancun.

Hoblit, who produced and directed the pilot, has chosen to stay in a hotel with no telephone. Eventually he is tracked down and Bochco, the executive producer, chats noisily with him behind his closed office door.

Bochco knows full well that his new series will be compared to "Hill Street," which after five years has achieved the status of television classic.

"Of course it will," he says. "Of course. I have a way of doing television. In fact, I would hope that there would be, in terms of perceptions, in terms of style, some continuity to my work, a kind of evolution to what I'm doing, and to the degree that that may be recognizable in the work, I'm not disturbed about that.

"But this is a very different show, in this sense, I think: 'Hill Street' for me always was fundamentally a series about despair, an extended story about people doing everything in their power to keep despair at arm's length. This new show is not about despair. This is an upscale show about by-and-large successful people who impact on the environment, often in a very positive way. They have some power, they have some money, they win battles, they lose battles, they compromise some, but in general they would tend to feel they're impacting on their environment.

"And so we have designed a show that reflects that. In terms of its look, in terms of its tone, it's not as dark. I think there are a lot of substantial differences."

Instead of the grubbiness of the Hill Street Station, "L.A. Law" takes place in the glassed and paneled labyrinth of a lucrative Los Angeles law firm. Jerky hand-held camera movements are out, gliding pans are in. In addition, the series is being edited in a relatively new way; it's shot on 35mm film, the film negative is transfered to tape, and the program is edited and color-corrected electronically. The pilot has a pretty lustrous gloss. Like "Miami Vice," which it will follow on the NBC Friday night schedule, "L.A. Law" looks as good as the commercials that interrupt it.

Some NBC executives quietly worry whether Bochco will be able to get the kind of viewer-pleasing dramatic situations out of lawyers in their lair that he and his colleagues did out of cops in their bestiary. Bochco is not disturbed about that, either.

"The law," he says, "is endlessly entertaining." In terms of compelling conflict, he cites a chilling scene from the pilot in which a woman who had wanted to accept her husband's settlement terms for divorce changes her tune after her lawyer shows her filthy pictures of the husband's adulterous acrobatics. At a subsequent confrontation in the law offices, with both lawyers present, the claws come out. "You low-life degenerate!" growls the wife. "You punishing bitch!" snarls the husband.

Her lawyer sails a piece of paper across the table, and she says, "Chew on those numbers, you impotent piece of snot."

It may sound funny. It plays very scary on the screen.

"There is more legitimate violence, psychic violence, in that divorce settlement scene than you'll ever see in any shoot-out on 'Hill Street Blues,' " Bochco says, "because it is the kind of violence that's visited upon all of us in our real lives. Very few of us have ever been shot at, or shot people, on the street, but 50 per cent of us go through that tearing emotional experience. It's really recognizable. It's visceral. That's violence. People look at the scene and squirm and fidget. So I'm not worried." He smiles. "We'll be 'Miami Visceral.' "

Bochco has come through a painful separation himself. Not the usual marital kind. He is still married to actress Barbara Bosson, who played Faye Furillo on "Hill Street Blues." But both Bochco and Bosson left the Hill under circumstances that were hardly amicable. Bochco was forced out a year ago, and replaced as executive producer by MTM Enterprises, where "Hill Street" is made.

The reason given for the abrupt ouster was that Bochco repeatedly went over-budget on "Hill Street." But most TV shows go over budget. The whole thing seemed mysterious. It still does. Bochco says budgets were not the problem.

"It was almost nothing about money," he says. "You know what it was? It was a divorce. [MTM President] Arthur Price said that. He said, 'It's personal, it's like a divorce,' and that's about as accurate as it gets. It really was personal. I maintain an inordinate regard for Arthur Price, and I suspect he would have the same for me, but they just had to get me out of there. They had to get me out.

"I didn't feel I was in a personality conflict. I was looking forward to remaining at MTM. This show was to have been done there. But they didn't want me." Bochco does not want to be more specific than that. "In truth," he says, "the only thing that finally matters is, I'm gone, and they're surviving very nicely without me."

Bochco says he isn't bitter about the way he was treated by MTM, but is bitter about the way his wife was treated. "No, I didn't watch the show this year," he says. "I didn't watch, however, not because of me; I didn't watch because of Barbara. I felt Barbara was treated very shabbily, very shabbily, and if I carry any genuine bitterness, it is that I believe she was treated really meanly and shabbily, and I think they took a lot out on her to get to me.

"It just became a lot easier for me and Babs not to look at the show."

Bosson quit the series after angrily alleging that other, comparable cast members were getting raises and she was not. In addition, it appeared little was going to be done with the Faye Furillo character if she remained in the cast. Bochco refers to all this as the "bullying of Barbara" and says, "I hate that. People who could have and should have stood up for her, didn't.

"But for myself, life goes on. This is television. I had seven of the most productive years of my professional life at MTM. I see nothing to regret in that. As painful as it may be to leave places in which you're comfortable, the leaving is very often a great thing, because it challenges you, it forces you to deal with a completely new environment."

An MTM spokesman, asked to comment on Bochco's remarks, said it is company policy not to respond and that Price will not discuss the matter either.

Bochco says the company does not have the warm, family atmosphere it did when Grant Tinker, now NBC chairman, was running it. "I think that changed," says Bochco, who considers Tinker "a pretty elegant guy" and says, "I hope some day to be part of an organization that I will be an originator of, that will duplicate the kind of atmosphere we had at MTM."

While conceding that "we were always at war with the economic powers that be" on "Hill Street," Bochco says the program under his and Hoblit's tenure (co-creator Michael Kozoll dropped out earlier as co-executive producer) was "the most responsibly produced show in television. We put more on the screen in less time and with less money than anybody else could have done.

"L.A. Law" will cost a little less than the more than $1 million spent this past season on each episode of "Hill Street Blues," although the lush-looking pilot ran well over $3 million. These costs, however, include standing sets -- the vast law offices and a near-perfect replica of the L.A. district courtroom. As for Bochco, his deal with Fox is said to be the most lucrative ever made by a TV producer with a production company. "I didn't lose anything financially" when he left MTM, Bochco says.

While still at MTM, Bochco tried another series, "Bay City Blues," about a minor league baseball team. The team was a failure and so was the show. Its problem, Bochco says now, is that it was "a story about young, naive, relatively uneducated youngsters in what by any measure would have to be considered a relatively frivolous endeavor in which there was really, absolutely nothing at stake. Nothing."

Whereas there is plenty at stake in "L.A. Law." Its toughest audience will probably be lawyers themselves. Bochco doesn't expect them to embrace the show as if it were a warm puppy. Already at least one legal journal is preparing a dig, claiming the program not to be authentic.

Bochco says that in addition to Fisher, one writer and an associate producer are attorneys, too, and another lawyer will be retained as technical adviser. "But I don't think that will stop lawyers from taking shots at us every chance they get," Bochco says. "Still, so far, all the attorneys who've read the script are really quite taken. We did our homework well in terms of procedure."

His own view of lawyers, Bochco says, is that they are mercenary warriors we civilized creatures employ to do battle for us.

"The law has always fascinated me because morality has always fascinated me," he says. "I think lawyers in general tend to be a mistrusted segment of the population. And often for good reason. But I think we take the curse off it by providing some attorneys in the show you'll enjoy hissing at and also some who care a great deal about what they're doing and are fundamentally decent. It's a good mix.

"In the course of time, what we may be able to expose is the almost numbing frustration a lot of attorneys feel working in a system that gives them little opportunity for job satisfaction. It can be really frustrating work. There's a lot of coitus interruptus; they gear themselves up for a big case and bang, it's settled on the courtroom steps and they're left holding the bag. Then there are the criminal attorneys who have to represent scum buckets. These are all real rich things for us."

Not that "L.A. Law" is only about lawyers. "It's about you, it's about me, it's going to be about any adults who function in a society that periodically frustrates them, forces them to compromise."

Hmmm. "Numbing frustration," "compromise," "little opportunity for job satisfaction." It sounds like an affliction common to those who work on episodic TV. Bochco says he doesn't see it that way. His office is not the place to hang out if you're in a trash-television mood.

"I think this is the most extraordinary medium that exists," Bochco says, leaning forward for emphasis. "You know, I have zero interest in working in the movies. None. Zero. Periodically, I'm solicited to work in the movies. I have no interest. Overwhelmingly, features are a director's medium. I'm not a director. It is a medium geared to a demographic profile I have very little to say to. The audience I want to address doesn't really go to the movies very much. They stay home and watch television. In great numbers.

"I think week-in and week-out, a show like 'Hill Street' or 'L.A. Law' will be doing much more complex work than anything you see on movie screens. We're doing it here. We're making 22 hours in the most powerful medium that exists. That's thrilling! That's heady stuff! And it also gives us a good perspective about our work. Because we have to do it quickly. We have to get it out there. We get it up on the screen and good, bad or indifferent, we've got to move along. It doesn't give us a whole lot of time to contemplate our bellybuttons."

It's a nice speech. Persuasive. Passionate. And son of a gun if Steven Bochco doesn't appear to mean it.