FILMS THAT Got Away, a series devoted to new movies denied theatrical release -- or released only sparingly or ineffectively -- was initiated at the American Film Institute Theater a few years ago by Michael Clark. Immediately popular, the series was renewed from time to time. Now Clark's successor, Eddie Cockrell, has renewed it on weekends, and the latest edition of "Films That Got Away" may become a permanent feature of the AFI Theater repertory.

The vagaries of distribution in the film business make such a series increasingly necessary. The first two movies shown during the current series, Martin Brest's "Hot Tomorrows" and James Bridges' "September 30, 1955," illustrate typical problems.

Although it is one of the most original and exciting movies of the decade, "Hot Tomorrows" was made under circumstances that still prevent it from being distributed commercially. "September 30, 1955" (the title refers to the day James Dean died; the movie depicts the effect of the tragic news on young people who idolized him) is seriously flawed but nonetheless compelling because of its subject matter and autobiographical nature. It was released in a few markets and previewed in others, but was quickly withdrawn when the distributor, Universal, detected little commercial or critical enthusiasm.

Divorced from the theater business and confronted with higher advertising expenses, the major distributors frequently find it more economical to write off pictures that fail to promise an immediate return on their investment. In many cases, the studio executives are probably justified. Still, it's demoralizing for filmmakes and unhealthful for the business when all opportunity to reach a public ends after a movie suffers a few bad previews or bookings.

Movie enthusiasts nurture an ongoing interest in the medium and its participants that transcends the quality of any given film. Like car buffs, they may cherish certain years or models, or even grow fond of obvious klunkers. For example, I have no reson to doubt that John Milius' "Big Wednesday," one of the selections in the AFI Theater series, was a fiasco -- but it's a likely fiasco I'm still eager to see.

"Hot Tomorrows," which began the AFI Theater series last weekend and will be revived at least once a quarter, is perhaps the finest example imaginable of a movie that deserves a public but can't attract one conventionally. It's the epitome of a great one that mustn't be allowed to get away.

Martin Brest will make his official feature debut this Christmas as the writer-director of "Going in Style," a comedy costarring Art Carney, George Burns and Lee' Strasberg as elderly cronies. "Hot Tomorrows" was his unofficial first feature, shot in 1975 under the auspices of the AFI's Center for Advanced Film Studies in Los Angeles and completed in 1977. It's a brilliant lyric comedy about the vanity of intellectualizing over death when confronted with its stark fact and certain mystery.

Brest demonstrated a stylistic assurance that both old pros and aspiring newcomers might envy, seeming equally adept at intimate, realistic depiction and expressionistic fantasy. Coming from a 23-year-old-student filmmaker, this display was electrifying. Few directors have ever revealed such a powerful affinity for the illusion-making and emotion-stirring potential of this medium.

The story takes place among exiles in Los Angeles on Christmas Eve and Christmas morning. The principal characters are young men named Mike and Lewis, played by Ken Lerner and Ray Sharkey, respectively. "Sharkey, potential dynamite as a screen actor, later appeared as one of the unforgettable thugs in "Who'll Stop the Rain,") Childhood pals from the Bronx, the boys are reunited in L.A. when Louis drives out to spend some time with Mike, or Mikey, as he persists in calling him.

The friends are temperamental and intellectual opposites. Mikey, an aspiring writer, has become obsessed with the idea of death. He is writing a story about the death of his grandfather, and attends a lecture series called "Philosophies of Death." Mikey can't even watch Laurel & Hardy in an old film without remarking sardonically, "Hey, Louis, you know what we're doing? We're watching two dead people."

His simple enjoyment ruined, Lewis protests, "What is it with you?" Mikey replies, "That's what's so great about old movies. You get to enter the land of the dead." Like many lines in Brest's tangy, ingeniously plotted screenplay, this one is calculated to come back and haunt us.

During an evening of melancholy fun-seeking, the gulf between Mikey and Lewis widens. Goofy, affable, non-cerebral Lewis knows that his friend's morbid streak is downright unhealthful. At first, he tries to joke about it ("You're so curious about death, I'll send you a postcard when I get there."). But as the evening wears on, his good nature wears thin.

The friends part on bad terms, although Lewis makes a desperate attempt at reconciliation. After Mikey drives away, Lewis looks sick at heart. Perhaps the most beautiful moment in Sharkey's endearing, sensationally inventive performance is his reading of this heartbreaking parting remark. "Maybe I should have stayed home for Christmas and come out here in January."

While dreading it, one might be able to anticipate the climax. Brest certainly prepares for it with seemingly casual and funny yet loaded dialogue and with deftly arranged episodes and motifs foreshadowing some tragic occurrence. What one could never ancticipate is the breadth and originality of the film's denouement, which takes a fantastic leap beyound simple pathos.

Brest plays absolutely fair with the audience. Every emotional surge, every ironic displacement from actuality to metaphysical fancy is anticipated in the plotting, dialogue and illustrative details. Still, the conceptual audacity of Brest's finale catches you off guard. Brest has taken the famous Brendan Behan taunt, "Oh death, where is they sting-aling-aling?" and given it a soaring lyrical send-off. When Hot Tomorrows" ends, you stare at the darkened frame in lingering amazement, still quivering with emotion at the fusion of pathos and spiritual elation just achieved before your astonished eyes.

Itching to shoot a feature when he entered the AFI, Brest found himself stymied by institutional protocal: Due to some unhappy early attempts to subsidize independent features -- and the suspicion engendered by such efforts in Hollywood -- the AFI had decided to back only short student projects. No productions were supposed to exceed a budget of about $10,000 or a running time of about 30 minutes.

In the grip of an irresistible artistic demon, Brest decided to shoot a feature-length version of "Hot Tomorrows" while pretending to be making only a short. He completed the shooting in four hectic weeks, but his little secret ended as soon as it became known how much footage was waiting to be developed at the labs. Despite the understandable consternation, Brest was allowed to assemble his indiscretion, which emerged as an inspired 73-minute feature that impressed most of the people who saw it.

Warner Bros. donated the funds to pay for the film's additonal costs, which overshot the AFI budget by about $20,000. Since many expenses were deferred or services rendered free, it's misleading to think of "Hot Tomorrows" as a $30,000 masterpiece. The hidden costs might multiply that figure about 10 times. Still, it would remain quality filmmaking at bargain rates.

The most serious hidden cost is the inability to distribute the movie widely. A non-union production, "Hot Tomorrows" needs clearances from all the movie guilds and crafts before it can be distributed as an ordinary commercial release. The idiosyncratic black comedy -- filmed in black-and-white and running shorter than the average feature -- probably would never achieve vast distribution. But potentially, it's the greatest midnight cult movie of them all, and at the moment commercial release remains foreclosed.

"September 30, 1955" isn't a masterpiece. Frequently awkward and inert, it's nearly stopped cold by a long, pivotal sequence in the middle of film that takes place in surroundings so dark that one can't discern what's going on. Gordon Willis' cinematography, shadowy as a rule, becomes utterly impenetrable for 20 or 30 minutes.

The movie gains a certain distinction because of its screenpaly and a surprising touching performance by the habitually overemotional Richard Thomas, who plays an Arkansas undergraduate deeply affected by the death of Dean, with whose screen image he identifies immensely. Portrait-of-the -filmmaker-as-a-young-man stories are rare enough on the screen and Bridges' autobiographical material seems unusually authentic.

After beginning clumsily and flirting with disaster, "September 30, 1955" rises to an unexpected level of pathos in Thomas' closing monologue. He describes his reaction's to seeing "rebel Without a Cause" to another obsessed fan, an impulsive girl who has suffered a terrible injury while attempting to pay tribute to the actor by staging a bizarre memorial service. The monologue must have run about 10 pages, but it's eloquently written and Thomas speaks it with stirring sincerity and urgentcy.

The public's identification with stars is, of course, a fundamental national phenomenon, yet it's seldom dealt with one screen -- let alone depicted with such heartfelt impact.

"September 30, 1955" is a borderline movie, and would probably be stronger in special circumstances -- i.e., double-billed with either "East of Eden" or "Rebel Without a Cause." The borderline cases deserve a shot, too. It's this sort of need that "Films That Got Away" promises to fill.