AN INTOXICATING blend of erotic and social comedy, Paul Brickman's "Risky Business" is brilliantly calculated to beam satiric illumination upon an open secret of adolescence. Inside every proud, doting mother's darling boy, it reminds us, there is a potentially lewd, lawless hedonist craving at least fleeting self-expression. Assuming the kid's self isn't utterly devoid of imagination or sex drive, of course.

Directing his own material, Brickman may prove to be an American original. There's not an ounce of visual or verbal slack in the picture. Brickman evidently met his directing opportunity knowing exactly what he wanted to achieve. The crispness of his verbal wit is reinforced by a pictorial style of equal precision and deftness.

Moreover, Brickman is one of those rare filmmakers who really orchestrate and control their effects throughout the duration of a movie. For example, there's a conspicuously haunting sound effect over the opening credits--the click of a commuter train speeding along its tracks--that not only echoes in certain later sequences but also underscores the end credits right to the very end. It's the last sound you hear, assuming you stick around to savor this lingering, gratuitous aural joke, and Brickman's style is full of such ingeniously planted and conscientiously cultivated motifs. He's such a smoothie that the motifs don't seem belabored; they are developed.

When the movie begins, you're aware of a vaguely disorienting illusion in that opening credit sequence. The images are in slow motion, taken from an elevated commuter train moving through a cityscape at night. Presently, the incongruous aspect dawns on you: the night vistas are gliding by in slow motion, but the sound of the train is realistically accelerated.

This curiously disembodied effect is then carried over into the dramatic texture of the story itself. Tom Cruise as Joel Goodsen is introduced describing an erotic dream, in which he enters a neighbor's house, discovers the baby sitter showering in steamy, DePalmaesque rapture in the bathroom and then loses sight of her, deflated by another intrusive fantasy that reminds him not of the pleasures of the flesh but the obligations and anxieties of the classroom.

Brickman establishes an atmospheric flexibility that allows the plot to manuever with surprising freedom between fantasy life and a fantasy-inspired and then complicated reality. It's not as if the outrageous situations Joel blunders into as a consequence of trying to gratify his teen-age sexual cravings are meant to be figments of his imagination; they happen, all right, and put him in the soup with hilarious authority, but they still partake of an ever-present dream reality.

One of the abiding jokes of "Risky Business" is that Joel's parents, impersonated with dreamy solicitude and obliviousness by Janet Carroll and Nicholas Pryor, never do know what a mistake they make when they leave for a week's vacation in Florida and trust their only child to look after himself and the house.

The setting is a well-to-do Chicago suburb called Glencoe, represented by Highland Park, where Brickman himself grew up. Attractive, clean-cut and agonizingly virginal, Joel is a better-than-average but far from exceptional student, anticipating a college future of some kind. His parents would prefer the Ivy League and have, in fact, arranged for him to be interviewed by a Princeton scout during their absence. Joel's pals urge him to abuse the folks' trust by taking advantage of his freedom from supervision while the opportunity lasts. The argument is expressed most cogently by his friend Miles, played by Curtis Armstrong: "You've got to be able to say, 'What the f---.' Saying 'What the f---' gives you freedom. Freedom buys opportunity and opportunity makes your future."

Joel's inhibitions tend to nip his fun in the bud. After all, even his dreams have a way of dissolving in self-censorship just when the good stuff is about to happen. On his own, he indulges some preliminary guilty pleasures, sampling generously from dad's bottle of Chivas Regal, taking the Porsche for a forbidden spin and blowing off steam by turning the stereo way up to mime a Bob Seger number.

Joel probably wouldn't stray beyond these tentative indications of mischief if left to his own devices. It's Miles who eggs him on to major vice and potential disgrace by making an appointment with a call girl. This presumptous prank turns Joel's life inside out when a call girl named Lana (Rebecca De Mornay) subsequently appears, transforms his erotic dreams into erotic gratification and then obliges him to master a crash course in free enterprise when she decides to borrow the Goodsen residence as a temporary haven and base of illicit operations.

Brickman arranges, complicates and resolves this improbable turn of events with considerable ironic finesse. Lana's incursion is a far-fetched situation rationalized by a tangle of motives and actions that unfold quite logically in terms of the story itself. Brickman also knows how to extricate the characters from this tangle in a satisfying way.

The casting and acting is uniformly excellent, but in Tom Cruise the movie probably has a new star to conjure with as well. Cruise had featured roles in "Taps" and "The Outsiders," but neither was calculated for the ingratiating, authentic range of youthful responses he projects in this role. RISKY BUSINESS

Written and directed by Paul Brickman; directors of photography, Reynaldo Villalobos and Bruce Surtees; music composed and performed by Tangerine Dream; produced by Jon Avnet and Steve Tisch. A Geffen Company release. Rated R. THE CAST Joel .. . . Tom Cruise Lana . . . . Rebecca De Mornay Miles . . . . Curtis Armstrong Barry . . . . Bronson Pinchot