American filmmakers must encounter businessmen as often, if not more often, than any other professional group. Professional survival, intact, demands they acquire some business experience and judgment.

Ironically, this business-saturated form of popular dramatic art rarely uses businessmen as protagonists or business life as a setting for drama. Perhaps they're too close at hand to feed the heroic fantasies that fuel most of our films. This season, when two of the major releases, "Blue Collar" and "F.I.S.T.," deal with labor, business seems to be represented exclusively by "The Betsy."

But in the movies directed by the remarkably astute French filmmaker Claude Sautet, businessmen frequently appear as protagonists. Yves Montand gave his most satisfying movie performance as the junk dealer in Cesar and Rosalie."

Now Michel Piccoli contributes an exceptionally persuasive starring performance to a strong, engrossing new Sautet film, "Mado," in which he portrays a developer simultaneously entangled in a business intrigue and a doomed infatuation.

Piccoli's character, named Simon Leotard, is stunned by the suicide of a friend and business partner, Julien. Soon he discovers that Julien has left a number of bad debts, all payable to a notorious financier named Lepidon. Simon and Julien's other surviving business associates must decide what to do about the debts.

A possible solution is suggested from an unexpected source: Mado, a determined young woman supporting herself and a sweet, heedless, pregnant roommate by working as a call girl. Simon is one of her regular clients. In fact, he is crazy about Mado, who does not return his love. But she puts him in touch with another client, a fugitive felon named Raymond Manecca (portrayed with crisp, amusing arrogance by Charles Denner) who is privy to information that can be used against Lepidon and willing to reveal it for a price.

Manecca proves vital to Simon's hopes of outwitting Lepidon, but their collusion also has tragic repercussions, which leave both Simon and Mado emotionally scarred and blast whatever fond illusions he retained of ever securing her love.

Many American filmmakers may prefer to identify with other classes even when their own habits and standards are obviously competitive and middle-class. Sautet doesn't need this pretense. His originality and importance derive from his open emotional identification with middle-class characters, particularly middle-aged businessmen faced by professional or romantic crises.

Sautet's view of life seems fundamentally tragic, or at least tragicomic. He doesn't perceive an easy social solution to the traps his characters fall into. There's never the faintest suggestion that people would cease messing up their lives if capitalism were abolished. At the same time hs tangled, messy bourgeois world is full of conviviality, loyalty and enduring affection. The compensations and disappointments are authentically mixed up and interdependent.

Sautet has contrived to summarize has social vision in the course of an ingenious and brilliantly sustained climatic sequence. Celebrating the success of his scheme against Lepidon, Simon and a party of friends visit the site of a projected new suburban development. Caught in a rainstorm, they take refuge for several hours at a local inn where a wedding reception is in progress. Attempting to return to Paris, they take a wrong turn and get bogged down in muddy sideroads.

They're stuck, and in more ways than one, but Sautet doesn't stop there. Bogged down and mud-spattered as they are, the characters try to make the best of things. They find shelter, build a fire, set out to find help. The giddier members of the party even pick up where they left off at the wedding reception and begin dancing to music from the car radios.

It's an extraordinarily funny and touching spectacle of middle-class friends coping with adversity. Sautet's characters are caught in the mire of existence, but most of them retain too much will and vitality to give up. There are exceptions, like Julien, and people bold enough to take dangerous initiatives, like Simon and Mado, may pay especially heavy dues in their emotional lives. Nevertheless, it's a livable, creative mire they're stuck in.

Some directors and cinematographers work together often enough to achieve an intuitive, supple visual rapport. Sautet and Jean Boffetty seem to have reached that point. "Mado" reflects absolute, unemphastic visual assurance from the opening shot. These filmmakers never groupe for the most filmmakers never groupe for the most expressive vantage point, the right timing, the right punctuation. They're right where they belong, clarifying a world that most of us belong to.