Michael Klein, a 52-year-old executive known as the Home Appliance King, switched off the lights in his cavernous office, took a private elevator to the gusty rooftop of his fortress-like corporate headquarters here and caught his evening ride across town -- in a helicopter.

Beefy bodyguards guided Klein into the dimmed cabin of his midnight blue Agusta A119 Koala. Within moments, it lifted off, joining other airborne limousines darting over the hazy skyline. Klein is one of hundreds of new helicopter commuters in Sao Paulo, the world's fourth-largest metropolis, where the rich and powerful soar high above exploding urban ills.

En route to his mansion in Alphaville -- a walled city where the privileged live behind electrified fences patrolled by a private army of 1,100 -- Klein quietly stared out the window. His pilot clipped low over the honeycomb-like slums and clogged highways below. More than halfway through a nine-minute commute, the copter grazed over a cluster of inner-city prisons. A squad of machine-gun-toting guards stood near a perimeter wall, their gaunt faces squinting upward as Klein's copter buzzed by.

"The perspective is different from up here," remarked Klein, a graying hulk of a man and executive director of Casas Bahia, one of Brazil's largest electronics retailers. Over the din of the blades, he told a reporter that "it even looks beautiful sometimes. Up here, however, it is safe. Down there -- ." He paused, staring across the metal and glass horizon. "Well, it's another story."

Sao Paulo -- a city of 18 million, populated by the fantastically wealthy and the severely poor with little in between -- is, by some accounts, a vision of future urban life in the developing world. As homicide and kidnapping rates have soared to record levels, civilian helicopter traffic here has become what industry executives describe as the busiest on Earth. Helicopter companies estimate that liftoffs average 100 per hour. The city boasts 240 helipads, compared with 10 in New York City, allowing the rich to whisk to and from their well-guarded homes to work, business meetings, afternoons of shopping, even church.

It is, sociologists here say, a sign of the way urban society in Latin American's largest nation is changing. Amid rising crime and overpopulation, the rich are retrenching into hyper-insulated lives.

In this sprawling nation of 170 million, sociologists call it the price of social inequity. Brazil has one of the most marked disparities of wealth in the world, with the richest 10 percent of the population controlling more than 50 percent of the wealth, while the poorest 10 percent control less than 1 percent. The disparity is particularly visible in Sao Paulo, a financial and commercial capital where many of Brazil's richest people live and work.

One result is city life dominated by fear. The homicide rate in greater Sao Paulo, South America's largest city, has more than tripled during the 1990s, to about 60 murders per 100,000 residents, compared with 7.4 in the Washington metropolitan area and 7.8 in New York. Already 63 kidnappings have been reported this year in Sao Paulo, up from only 15 during the same period last year, according to police statistics. The surge in abductions has produced a cottage industry of plastic surgeons who specialize in treating wealthy victims who return from their ordeals with sliced ears, severed fingers and other missing body parts that were sent to family members as threats for ransom payment.

Despite a lackluster economy, a $2 billion-a-year security industry is thriving across Brazil. Brazilians are armoring and bulletproofing an estimated 4,000 cars a year, twice as many as in Colombia, which is in the midst of a 38-year-old civil war. A wealthy Sao Paulo businessman, who spoke on the condition his name be withheld, said he allows his daughter to boogie at nightclubs only under the eyes of a commando turned bodyguard. In a city where the wealthy are known for ostentation, many are now buying low-profile economy cars to fool kidnappers and thieves.

"We have become prisoners in our own homes," said Ellen Saraiva, the elegant wife of a construction magnate, as she sat in her tasteful living room in a heavily guarded building in Sao Paulo's fashionable Jardims neighborhood. After a series of high-profile kidnappings on nearby streets last year, she and her husband paid $35,000 to bulletproof their understated gray Volkswagen. The armoring cost twice as much as the car.

"I pray to God every time I leave my building," she said. "I live in fear for myself and my family. One of my daughters is studying abroad right now, and as much as I miss her, it makes me feel at peace to know she is not here living through this nightmare."

Sao Paulo experienced an industrial boom over the past century, luring millions of poor Brazilians from the destitute northeast to settle here. Most traded destitute rural lives for urban misery, piling into ever-growing slums that have become dens for gangs dealing in drugs, kidnapping and arms.

Many of the wealthy have responded by moving into guarded, walled communities such as Alphaville. Only 7 1/2 miles from the city center, Alphaville is home to 30,000 of Sao Paulo's most privileged residents. It has three helipads and four entrances and exits, all monitored 24 hours a day.

Inside the compound, visitors are recorded by cameras at guard checkpoints in residential zones. In the communal areas, children can attend well-guarded schools and enjoy afternoon sports on fenced-in fields watched over by Alphaville's black-clad security guards. At night, on "TV Alphaville," residents can view their maids going home for the evening, when all exiting employees are patted down and searched in front of a live video feed. The local gym, which specializes in self-defense classes, is called CIA. To enter the local shopping center, customers must first pass through a guarded gate.

"The elite have made a decision. Instead of looking to better Brazilian society in general, they are abandoning it and finding their own personal protection behind guarded walls," said Teresa Caldeira, a noted Brazilian anthropologist and author of the book "City of Walls: Crime, Segregation, and Citizenship in Sao Paulo." "The rich are retrenching, restricting their lives in incredible ways and living their lives in an increasingly paranoid fashion."

Carlos Polacco, a Sao Paulo sailboat dealer, calls his decision to move his family to Alphaville in 1998 an issue of survival. The family bought its elegant, nautical-themed home here after the Polaccos' grown son, Rodrigo, was kidnapped while driving in the city. After he faked a heart attack, his abductors stripped him of all but his boxer shorts and threw him from a moving car.

"This is not about sealing yourself away from the rest of the city," said Polacco, who enjoys sailing to ports across the Atlantic seaboard. "But the violence has forced us to change our lives. When I thought about the chance of losing my son, I realized that we had to do whatever was necessary for our protection. This place gives you a chance to exhale."

A recent study by Veja, Brazil's largest newsmagazine, found that the number of Brazilians living in walled communities doubled to 1 million over the past five years. Sao Paulo has more than 300 such communities.

Heloisa Leuzinger, 40, an English teacher whose husband is a banker, moved into another closed community just beyond Alphaville about 18 months ago. As a woman who grew up in Rio de Janeiro and revels in urban life, she worries that her two young children "are growing up in a bubble."

"They go to school here, they play here, their friends are here," she said. "When we go into the city, the older one sometimes asks, 'Mommy, why is that man begging?' or 'Why do those kids live on the streets?' I try to explain to them about the social injustices, but I worry sometimes that they are living sheltered lives.

"But I have no choice but to risk that," she continued. "Their safety comes above all else."

The helicopter craze here started in the early 1990s, initially in response to safety concerns, but also to frustration with traffic. Public transit is woefully lacking -- the subway system is far smaller than Washington's while serving a population four times as large -- and highways are clogged and narrow.

As organized crime in Sao Paulo has increased, with the rich almost always the target, helicopters became a way to safely travel across town. Owning your own helicopter, however, is only for the wealthiest residents. The most basic models cost more than $400,000, and more lavish ones run $2 million and up.

But "helicopter collectives" have popped up. At Sao Paulo's Helisolutions, more than 100 members share the costs of purchase, maintenance and pilot time on a fleet of copters. It brings the price down to a one-time fee of $40,000 along with monthly expenses of about $1,500.

Klein uses one of his family-owned company's two helicopters. He hops in for daily commutes, trips to the company's distant warehouse and excursions to business lunches in the city, where nearby helipads are sometimes easier to find than a good parking space. Convenience is one reason, but safety more so.

"Here in my building, I know I'm safe," he said. "At home, I'm safe. But once I leave, I need other ways to have peace of mind."

Special correspondent Nadejda Marques in Sao Paulo and researcher Robert E. Thomason in Washington contributed to this report.

Michael Klein, chief executive of a Brazilian retailer, commutes via his company's helicopter in Sao Paulo.A helicopter approaches a landing area in Sao Paulo, where executives are routinely flown between home and work.