A dozen years ago, 22-year-old Divino Cardoso Campos quit his job as a store clerk in a small town, crammed his possesions into a knapsack and set out to try his luck in Brazil's untracked western frontier.

Here, at kilometer 1,032 of the unpaved Marechal Rondon highway, in the middle of Amazonian wilderness, the truck in which he had hitched a ride got stuck in the mud.

What followed was one of the histories of chance, enterprise and sudden fortune that have made this territory the site of one of the world's most spectacular human migrations. Stranded along the road for several days, Cardoso struck up a friendship with a local pioneer farmer. When a small settlement was cut out of the bush a year later, he came back from the nearest town to peddle perfume and silk door-to-door.

Today the former itinerant clerk is the wealthy owner of two modern department stores and the newly constructed Cacoal Palace Hotel. The virtually untouched wilderness he headed for has become the state of Rondonia, and Cacoal a boom town of 60,000 whose population is doubling every year.

Last month, to top it off, the final stretch of deep red soil on the 880-mile Rondon highway was paved outside of Cacoal, ending an era of quagmires that shaped the lives of Cardoso and tens of thousands of other pioneers. "This is a place that has gone from wilderness to shacks to a city while I've been here," says Cardoso, attired in an open shirt, gold watch and gold neck chain in his air-conditioned office. "We're still only getting started."

The completion of the highway from Cuiaba, the capital of Mato Grosso state in west-central Brazil, to Porto Velho, a river port in the Amazon basin and capital of Rondonia, has been celebrated in Brazil like the opening of a western railroad in the United States 100 years ago.

President Joao Figueiredo travelled from Brasilia to inaugurate the route. Politicians, businessmen and the national press portrayed the event as a herald of their country's vast potential amid the gloom of a prolonged economic crisis.

Already, this corridor through savannah and jungle just north of Bolivia has become one of the few areas in South America's vast interior to trigger a major surge of development. About 320,000 settlers passed down the Rondon highway between 1979 and 1983, and 120,000 more arrived in the first eight months of this year.

Now, tens of thousands more are expected to come down the finished road, abandoning depressed towns or migrant farm work in Brazil's southern interior for dreams of fresh land and jobs and a rare chance to move up in life.

Already, federal officials in Rondonia, though boasting of the region's astonishing growth, find themselves trying to check the flood. "The numbers are so great that it's starting to get out of control," said Ernani Carvalho, the regional coordinator of the government's National Institute for Colonization and Agrarian Reform.

The perils of the expansion are enormous. Uncontrolled settlement could quickly strip this state of its vast reserves of fragile tropical forest, exterminate its wildlife, and endanger its tribes of native Indians. Officials warn that most of the best farmland along the highway already has been parceled out and new settlers must now wait two or three years for a chance to be given a fresh piece of federal land -- if they qualify.

The attraction of this region, however, is not only its relatively rich tropical soil. In contrast to most of the rest of the country, Rondonia's land has been handed out by the goverment in small parcels to single families. Most tracts are less than 250 acres, and authorities have even expropriated some large estates once held by rubber barons so that they could be turned over to landless peasants.

The highway corridor consequently has come to be known as a relatively egalitarian frontier where anyone can make a fortune. That incentive alone appears to have had a greater effect on migrants than any lure of official settlement projects.

While the celebrated Trans-Amazon highway in northern Brazil has virtually shut down from disuse and many colonists selected, recruited, transported and paid salaries by the government have given up and gone home, the Rondonia settlement has been carried out by people who found their own way out to the jungle.

Their modern wagon trains have been convoys of buses that load up in southeastern states like Minas Gerais and Parana and strike out down the Rondon highway dozens of times a day. The bus passage from Cuiaba to Porto Velho -- roughly comparable to a trip from Washington to Montreal -- now costs $14.

The journey has not always been easy. Before the highway was paved, buses routinely took 30 days or more to reach Rondonia from Parana state. During the rainy season, four months a year, much of the road would be churned into a mud pit and, once stuck, buses could be trapped for days.

Drivers still tell tales of delivering babies in the aisles of their packed carriages or building fires at night in lonely stretches of wilderness. Today, they must navigate the narrow highway amid myriad trucks, carts and flocks of animals and dodge the men on horseback and on foot.

Along the road in Rondonia are towns of dusty red streets and stained wood storefronts where housing is improvised, schools scarce, and malaria rampant. But jobs are plentiful.

In Cacoal, an average of more than 2,500 new settlers per week have been registered this year in the town and surrounding municipality.

Mayor Josio, Brito and most of the town's other leaders are unabashed boosters of even more rapid growth. "We want people to come here," Brito said. "Our problem is not unemployment; it is shortage of labor. No one here is hungry. Anybody who wants to work can come here and get a job."

Brito, a former teacher, has another success story. He migrated to Rondonia and worked as a mine laborer before becoming one of the first settlers of Cacoal in 1972. He was granted a tract of land, and soon opened Cacoal's first pharmacy and became its justice of the peace.

Now he is a prosperous pioneer of the politics and affluent social life of Cacoal.

"I saw a new opportunity in a new place, so I dropped what I was doing and came here with a few other people," Brito said. "It turned out we were right about this place."