The show business romantic farce "Tootsie" is an opportunistic, tangy, comic rabble-rouser.

Primed (even overloaded) to bring Dustin Hoffman his second consecutive triumph in the role of a man who allegedly transcends failure by acquiring womanly attributes (in the Oscar-winning hit "Kramer vs. Kramer," adversity put Hoffman in improving touch with the maternal instinct), "Tootsie" suggests the path to virtue requires a female impersonation.

The hero of "Tootsie," a flaw-ridden but eminently actable contrivance credited to Larry Gelbart, is an intent, fortyish Broadway actor named Michael Dorsey. Dorsey has acquired a reputation for being difficult, which has made him nearly unemployable as an actor. His big break materializes after a colleague and student, Sandy Lester, played by Teri Garr, blows an audition for a leading role on a soap opera, "Southwest General."

Impulsively, Dorsey dresses up the next day and auditions successfully for the same role, a schoolmarmish hospital administrator. Nothing if not assertive, Dorsey wins the part, under the alias Dorothy Michaels, by standing up to the overbearing director, Ron Carlysle (Dabney Coleman). The homely but forthright dignity "Dorothy" projects in her encounter with Ron becomes the keynote to her characterization on "Southwest General," which transforms her into an overnight sensation and the working girl's heroine.

Dorsey's little secret is known only to his droll playwright roomie, Jeff, played by Bill Murray, whose work-in-progress, "Return to Love Canal," stands to benefit from Dorothy's income, and to his nervous agent, George, played so expertly and likably by director Sydney Pollack that he should now be in constant demand for certain solid, affable character types.

Although an imposing public success, the imposture begins to seem an insupportable burden when Dorsey fears that he may be stuck with it indefinitely and that it will prevent him from competing honestly for the romantic attention of "Southwest" leading lady Julie Nichols (Jessica Lange in a performance of considerable charm, marred by only one miscalculated touch, her oddly cavalier identity as the unwed mother of a year-old daughter). The frustration is enhanced when Julie's father, Les (Charles Durning), a widowed farmer, reveals a hopeless infatuation with Dorothy.

In certain respects, Dorsey's masquerade really becomes Hoffman. He looks absurdly cute in Dorothy's dressy get ups and owlish horn-rimmed specs, rather like Andrea Martin of the SCTV troupe when assuming her Edith Prickley character. The twittery voice Hoffman affects for Dorothy is also amusing as far as its thin expressive range permits--not all that far compared to what a comic actress can do with her own voice, of course. Teri Garr demonstrates that range with a decisive flourish during her greatest movie scene yet, a delightfully infuriated monologue in which Sandy blows up at Michael for his deceitfulness and storms out the door on a ringing exit line.

In fact, it seemed to me that Hoffman's act generated more problems than pleasures after the initial comic impact began to wear off. Dorothy has greater dazzle in stills than as a sustained motion picture character, a point emphasized by the fact that Hoffman has his funniest takes when striking poses for Dorothy's cover girl appearances on a succession of magazines.

However, the most nagging impediment to wholehearted acceptance of "Tootsie" and its little storytelling subterfuges is a failure to recognize the hypocritical aspects of Dorsey's imposture and alleged character improvement. Although Dorsey is supposedly sensitized to the desirability of honesty and consideration in romantic dealings by being forced to seethe on the sidelines while Ron treats Julie badly, the hero never does square things with Sandy, the woman whose trust he betrays in a far more deliberate, systematic fashion. Indeed, it seems downright outrageous for Dorsey to get indignant about Ron's oblivious sort of misbehavior when he's conning Sandy in premeditated ways.

The movie tries to finesse this disagreeable element by emphasizing the fact that Dorsey is eating his heart out for Julie and feels chastened by her understandable resentment when best pal Dorothy finally reveals her true identity and intentions during a tumultuous episode of "Southwest General."

The "Kramer" triumph seems to have given Hoffman the dubious notion that he has a special claim on redemptive feminine virtue. His approach to a reconciliation with Julie relies on assurances of enlightened consciousness as a result of pretending to be a woman--"I wasn't strong enough to be the woman who was the best part of my manhood" or "I was a better man with you as a woman than I was as a man with any other woman."

There was always a dubious element of masculine self-approbation behind the sentimental gratifications of "Kramer vs. Kramer." While it wasn't difficult to be stirred by the heroic spectacle of an abandoned husband's efforts to be both father and mother to his little boy, it was also difficult to overlook the fact that the runaway mother was never really in the picture.

Hoffman is now on the brink of overdoing the role-changing conceit that suggests men may improve their characters by emulating women. He tends to get especially sappy about this eminently modern self-delusion when putting it in So Many Words, like the lulus quoted above.

"Tootsie" has enough rowdy, inconsequential fun in it to take the curse off Hoffman's sentimentalized notion of The New Man, but it's also in the nature of a lucky tightwire act that comes close to tripping him up. Everything considered, he'd be well advised to quit while he was still ahead.