Carlos Diegues was a poet and movie critic before he began writing and directing movies in the early '60s, when he helped launch "Cinema Novo," the Brazilian equivalent of the French New Wave. His latest movie is "Bye Bye Brazil,'" Diegues has said, "is a film about a country which is about to come to an end in order to make way for another which is about to begin . . . Life today in Brazil often springs from the strange combination of the archaic and the modern, of the forest and pollution, of the ox-cart and the jet, poverty and affluence, beauty and pain, of the old and the new . . . a country that is still able to change its destiny through its own weirdness."

The movie derives its exotic fascination from the filmmaker's expansive comic vision of his country, a vast landscape and multiracial culture riddled with contradictions. At once innocent and corrupt, primitive and modern, inspiring and frustrating, the Brazil traced by Diegues' tawdry, amateurish troupe of provincial entertainers, the Caravana Rolidei, as they loop from the northeast into the central plateau and eventually disappear down a long, long highway into the west, is a wonderfully evocative epic setting. Unfamiliar in certain respects, the movie nevertheless strikes a familiar, stirring chord -- a frontier odyssey transposed to South America in the present.

The Caravana Rolidei is first seen rolling into the dusty town of Piranhas on the Sao Francisco River. The "caravan" consists of a venerable pickup that carries a very small company of itinerant performers: Jose Wilker (he was the dissolute, sexy husband in "Dona Flor and Her Two Husbands") as the feckless impresario and magician who calls himself "Gypsy Lord"; Betty Faria as Salome the "exotic" dancer, whose willingness to turn the occasional trick keeps the company in business; and Principe Nabor as the mute strongman Swallow.

Their performance before the undemanding residents of this rural river outpost reveals a beguiling tackiness. When an artificial snow covers the audience as a backstage phonograph plays Bing Crosby singing "White Christmas," the master of ceremonies sums up the pathos of this Big Illusion by declaring, "Yes, snowing in Brazil, like all the civilized countries of the world!" Guarding against possible small-town prudery, he introduces the bread-and-butter act, Salome's dance, by insisting cagily that "Salome is a dream and can only offend those who don't dream."

Gypsy Lord has a touch of the poet. In another small town we see how his confidence games can have a benign inspirational influence on spectators hard-up for diversion.He's a charlatan, weakling and sometime pimp who can nevertheless console a sorely deprived public in certain ways.

The troupe is seized upon by a dreamy, naive young peasant husband, Cico, who attends a performance. The next morning he says farewell to his father and volunteers himself as an apprentice to Gypsy Lord, who appears to accept out of storytelling convenience. Cico (Fabio Junior), accompanied by his accordion and pregnant wife, Dasdo (Zaira Zambelli), becomes a member of the fly-by-night fraternity. The augmented troupe struggles to make a living in the show-starved hamlets of a barely developed continent.

The movie begins to break down because Diegues seems to lack the ability to sustain his vision dramatically. "Bye Bye Brazil" remains a peculiarly appealing idea for a movie, but it's never adequately embodied in the characters or the conflicts that confront them.

Diegues' spare, detached, excessively deliberate pictorial style lacks the intoxicating exuberance and sensuality demonstrated by his precocious young countryman Bruno Barreto in "Dona Flor and Her Two Husbands," the first Brazilian feature to captivate American art-house audiences. Intellectual and ponderous where Barreto was intuitive and fluent, Diegues always keeps his distance. His characters have more identity as symbols than idiosyncratic, intimately observed human beings. The conception invites us along, but the execution leaves us stranded.

Even when it misfires, "Bye Bye Brazil" is headed in a direction that arouses considerable interest and sympathy. If only Diegues had been able to sustain the savory lyricism and eccentric comic tone of the early sequences, which seem to echo early Fellini. Their spirit is delightfully sustained in the haunting title song, written by Roberto Menescal and Chico Buarque, who also did the lyrics for the theme song in "Dona Flor and Her Two Husbands." Diegues has the makings of a great Brazilian national comedy, but the final, satisfying achievement eludes him.