Elisa Rey puts a wad of Japanese yen into a small, brown envelope at her home in the Japanese capital. Far away, in a poor district of Peru, the money she and her two brothers have sent has built a four-story house.

They can thank their grandfather for having emigrated from Japan to Peru a century ago.

Japan began importing unskilled workers like Rey to offset a labor shortage in the early 1990s. But given the importance it places on bloodlines, it would take only those who could show Japanese ancestry up to three generations back.

There are plenty of them, judging by the amount of money they are sending home -- more, by some estimates, than Japanese taxpayers spend on aid to developing countries.

"The surge has been spectacular," said Armando Ouchida, executive director of Convenio Kyodai -- a cooperative used by many of Japan's 52,000 Peruvian residents, the country's fifth-largest foreign worker community, to send money home.

The remittances go directly into building businesses and homes for poorer families and are increasingly touted by aid officials as an important development tool. Japan has emerged as a remittance juggernaut despite a proportionately tiny number of foreign laborers -- less than 1.5 percent of Japan's 53 million-strong workforce.

Japan is the world's largest foreign aid donor after the United States, dispensing 857.8 billion yen ($7.8 billion) in fiscal 2003.

But while official aid reaches its recipients via governments, remittances go straight to "the pockets of the poor people," noted Enrique V. Iglesias, president of the Inter-American Development Bank, who was visiting Tokyo.

Rey, who works in an electronics factory south of Tokyo, said she and her brothers send their parents about 40 percent of their monthly salaries. It's difficult to live on little more than half her salary, she said, but the house in the town of Chancay, just north of Lima, is worth the sacrifice.

"Now it's all paid off, we have something to go back to -- a home, a life," she said.

Rey came to Japan seven years ago and plans to stay for up to 10 more.

Takashi Kadokura, senior economist at Tokyo's Dai-ichi Life Research Institute Inc., estimated in a study last October that $5.5 billion is sent annually through unofficial channels by illegal foreign workers in Japan, primarily Chinese, Koreans and Filipinos.

Combined with the $2.77 billion in declared remittances recorded by Japan's central bank in 2002, foreign workers are sending out more than $8.25 billion annually.

Worldwide, such funds have proved a boon to developing countries.

Latin American and Caribbean workers sent home a record $38 billion in 2003 -- more than foreign direct investment and official aid to the region combined, according to the Inter-American Development Bank.

About $31 billion of that came from an estimated 14.5 million Latin American-born migrant workers in the United States.

Next came Japan, whose tiny 350,000-person Latin American and Caribbean community sent home $3 billion.

Remittances of about $2.5 billion from Japan to Brazil last year outstripped the value of Brazil's coffee exports. Peruvians made up only 2 percent of all Peruvian migrant workers living abroad but contributed 16 percent of the total $1.2 billion sent to Peru from the whole world.

Filipino workers in Japan remitted $413 million in 2003, making them the largest source after Filipinos in the United States and Saudi Arabia, according to the Philippines' central bank.

"Overseas workers are one of the pillars of the [Filipino] economy -- without it, there'd be no foreign reserves," said Brenda Tenegra, at Tokyo's Ochanomizu University, who researches Filipino workers in Japan. "Per capita, Japan is one of the largest remitters."

With foreign workers in Japan proportionately contributing more than their counterparts elsewhere, they are attracting interest as a serious source of financing. Projects are underway to help migrant workers better use their remittances to start small businesses when they return home, including a $12 million venture capital fund for Brazilian workers in Japan that provides seed capital and training.

With Japan's rapidly aging society facing a growing labor shortage and pressure from business lobbies to allow in more foreign workers, the flow of remittances is sure to grow.

Pilar Aniya, center, and colleagues pose at Convenio Kyodai's center in Tokyo. Remittances to Peru have surged in recent years.A staff member at Convenio Kyodai, a cooperative that helps many Peruvian workers in Japan send money home each month, takes a phone call.