LOS ANGELES -- It seems the long drought in summer movies for grown-ups is over. In the past six weeks, the major Hollywood studios have released four films aimed specifically at the over-25 viewer: "The Untouchables," "The Witches of Eastwick," "Roxanne" and "Full Metal Jacket." And surprisingly, all four films are doing extremely well at the box office.

With almost 40 percent of all box office receipts coming between Memorial Day and Labor Day, summer has traditionally been Hollywood's most lucrative season. And in recent years summer movies have pandered almost exclusively to the teen-age audience, largely due to the blockbuster success of such review-proof, youth-oriented films as "Ghostbusters," "The Karate Kid" and "Top Gun."

The huge receipts from those films discouraged Hollywood from taking a chance on more sophisticated material during the summer months. "The major studios like to play the favorites," said Tom Sherak, president of distribution for 20th Century Fox. "They figure 'if something's not broken, don't fix it.' "

Except for the occasional adult-oriented films such as "Prizzi's Honor" or "Heartburn" -- both of which did only fair business -- Hollywood has saved its more "serious" fare such as "Amadeus" and "The Killing Fields" for the fall and Christmas seasons. Adults have had two choices during summer: Either see youth films like "Back to School" or "Ferris Bueller's Day Off," or sit out the summer entirely.

But this year the major studios were forced to rethink their release strategy because of an unusually heavy crunch of product. Not only have the studios been making more films, they're also picking up more independently made movies, such as the Australian import " 'Crocodile' Dundee" (released by Paramount last fall) and "Ernest Goes to Camp" (released by Disney over Memorial Day weekend).

"The market is so crowded now that the seasons are all running together," says Robert Friedman, senior vice president for publicity and promotion at Warner Bros.

So rather than compete for the same viewer dollar, the studios have begun to focus on different audience segments. Two summers ago Warner Bros. went up against "Ghostbusters" with another youth-oriented adventure, "Gremlins." This summer, however, the studio opted to go up against Paramount's likely blockbuster "Beverly Hills Cop II" with the more sophisticated "Witches of Eastwick," starring Jack Nicholson and Cher and based on a John Updike novel.

"We knew that the prime audience for 'B.H. Cop' was young males," says Friedman. "Our target audience for 'Witches' was older females and males; so we took the chance and positioned the film in early June."

Paramount had so much confidence in the adult audience that it released "The Untouchables" within two weeks of "Beverly Hills Cop's" Memorial Day weekend debut. "Adults have always been available to us in summer," says Sidney Ganis, Paramount's president of marketing, "but the product hasn't always been there. We knew we could get the older audience with 'The Untouchables' if we got the kind of strong reviews and media attention we were counting on."

Both "Untouchables" and "Witches" received the kind of strong reviews necessary to launch them with a more selective audience of men and women over 25, and will probably end up among this summer's five top-grossing films.

Still, good reviews alone were not enough to make hits of such films as "Full Metal Jacket" and "Roxanne."

The former is a serious, uncompromising film with no big-name box office stars like Robert De Niro in the "Untouchables" or Nicholson. Warner Bros.' ace in the hole, however, was the film's star director, Stanley Kubrick ("2001," "A Clockwork Orange"). "Jacket" is his first outing since "The Shining" in 1980, which makes it an "event," said Friedman. "And when you have a serious film from a high-quality director like Kubrick, it immediately cuts its own path."

"Roxanne," starring Steve Martin and Daryl Hannah, however, is not an "event" movie. It's a small romantic comedy that could easily have gotten lost in the summer crush of big films. Fred Schepisi, who directed "Roxanne," says the marketing of the movie was as important to its success as good reviews.

"How Columbia Pictures advertised 'Roxanne' was probably the biggest gamble. They didn't want to send out the word that this was just a goofy Steve Martin comedy. It was important to emphasize the romance." The ploy worked, getting "Roxanne" off to a strong start. How well it will do in the long run depends on word of mouth. But Schepisi is not worried. "Ultimately a good movie speaks for itself."

Does the success of these four films bode well for adult fare in summers to come? "If we feel the film is right, we'll go with it no matter what time of year," says Jeffrey Katzenberg, chairman of Disney's film division. "Our rule of thumb is that there are no rules anymore."