KINSHASA, Congo -- Four years ago, a brother living in Switzerland sent Masamba Bienvenu a cell phone. The phone was intended for his personal use, but Bienvenu, an unemployed university graduate, had bigger ideas.

For $10 a month he rented a little tin-roofed storefront in Selembao, one of Kinshasa's poorest neighborhoods, and began allowing passersby who had no telephone of their own to make calls on his for a small fee.

Today he owns a half-dozen cell phones and runs three roadside shops catering to a steady stream of customers who stop by to call relatives, make business deals or find out if anybody's at home before taking an expensive taxi ride across town.

The $100 a month in profit he earns -- more than three times the average income in Congo -- has made him financially independent from his family for the first time in his life and even helped him attract a fiance.

"Thanks to this, I will get married," said the lanky 36-year-old, perched on one of his shop counters in a long tunic, carefully pressed pinstriped trousers and a pair of shiny black loafers. "The cell phone business has changed my life."

Cell phones are changing lives across Africa. On a continent where mail service is spotty, roads are bad and fixed-line phones have never really taken hold, portable phones are enabling people for the first time to keep in touch with faraway relatives, check market prices, cut better business deals and just plan their days more efficiently.

In South Africa, 85 percent of small black-run businesses rely solely on cell phones for communication, according to a study by the Center for Economic Policy Research in London. In Swaziland, HIV-positive patients rely on text messages to tell them when to take their medication.

In a growing number of African countries, the phones are replacing banks as a primary means of transferring money and paying bills. And taxes on cell phone providers and users are rapidly becoming one of the primary sources of government revenue for many sub-Saharan African countries, said Devine Kofiloto, an analyst with Informa Telecoms & Media in London.

The technology "is having a huge impact," he said. "It's not like it's come up as an alternative form of communication. Prior to this, there was nothing."

Africa today is the fastest-growing market for cell phone contracts in the world. In 1999, sub-Saharan Africa had just 7.5 million mobile phone subscribers; today 177 million Africans own a mobile phone and millions more make calls on rented or borrowed phones.

South Africa, a nation of 44 million people that is the continent's richest, is still its largest cellular market. But Nigeria, a nation of 132 million where the number of cell phone contracts has surged from 700,000 in 2001 to 25 million today, is poised to pass South Africa next year, Kofiloto said.

Growth in Africa "has exceeded everyone's expectations," he said. "The world market has definitely been surprised."

Africa's rush to cell phones began in the mid-1990s, when governments first began allowing private competition to state-owned communication services. But its growth has been driven not just by lower prices but by a desperate need to communicate on a continent where few alternatives to mobile telephones exist.

Across much of Africa, fixed-line phones are relatively few and don't always work reliably, especially after heavy rains or when thieves steal copper transmission lines for scrap. In many countries, the wait to have a phone line installed can be interminable.

Congo, for instance, a nation of 63 million people that sprawls over an area the size of the United States east of the Mississippi, has just 20,000 fixed-line phones, one for every 3,000 people. The country also has just 750 miles of decent paved roads, and traveling by river from one end of the country