When Avenamar Cruz thinks of Atopoltitlan, the little town in the Mexican state of Puebla that he left 19 years ago, he remembers the celebrations most of all.

In April, at the annual feast of the Virgin of the Rosary, he would watch the riding of the bulls, cockfights and fireworks. When townspeople were married, the whole town would gather at the bride's house to dance and sing. And at Christmastime, the statues of Mary and Joseph would be moved from the church every night to visit a different house, where a party would be thrown, with a piÒata and plenty of sweets for the children.

"The traditions of the town, the festivals, those are the things I really miss," Mr. Cruz said.

Now 36, he lives in the Bronx and works at the Hunts Point produce market. He may never return to live in Atopoltitlan. Even so, he continues to take an active part in the life of his town, helping to raise money for festivals, a basketball court, street lights in the town center and - most recently - a clean-water system.

Around the New York City region, Mexican immigrants like Mr. Cruz are getting together with others from their hometowns and chipping in as much as they can afford - $50 here, $100 there - to improve conditions in the poor rural towns they left behind. The projects range from sprucing up the town church to expensive public works.

According to Manuel Orozco, a senior researcher at Georgetown University who has been studying hometown associations since 1996, such groups contribute up to $60 million a year for public works in Mexico. That number, he emphasized, is over and above the money sent by people to their families.

In the New York region, water projects appear to be popular choices for hometown associations because many migrants come from the arid Mixteca region, which includes parts of Puebla.

"Here one gets used to turning on the tap and having water," Mr. Cruz said. "Over there, there's barely water to drink, let alone take a shower."

Mr. Cruz's group, Mexican-American Atopolteco (Atopolteco is an affectionate diminutive for the town's name), was started in January 2003, when a town official visited and convened a meeting in Passaic, N.J. At the meeting, Mr. Cruz and 10 others were chosen to head a committee to carry out projects in the town, and a similar committee was formed in Atopoltitlan.

While hometown associations have been common for decades in Los Angeles and Chicago, only in the last decade have these committees become more noticeable in the New York area. "I would calculate that there are about 20 or 30 groups, but this is not a completely reliable figure," said Consul Gaspar Orozco (no relation to Manuel Orozco), who is in charge of community affairs at the Mexican consulate.

Robert C. Smith, a professor at Barnard College, put the number of groups closer to 100 in the New York area. In his book, "Mexican New York: Transnational Worlds of New Immigrants," to be published at the end of this year, he documents the activities of a Brooklyn-based association that raised $100,000 to bring water to its town. "The dedication these men show is utterly amazing," Professor Smith said.

Nicol·s S·nchez, who is from San Miguel Comitlipa, in the state of Guerrero, says that he spends several hours a week coordinating with other committee members, raising money and consulting with people back home. So far, migrants here have paid for the town church to be painted in shades of white and blue, for an antenna so the City Council office can receive television signals and for school furniture and computers.

"I can do something for the place where I was born," said Mr. S·nchez, 32, whose mother still lives in the town. "It makes you feel good, like you have a purpose."

Yet the hometown groups sometimes find that they do not always see eye to eye with officials back home about how to spend their money.

"The migrants usually start with renovations or an aesthetic project," said Alex Rivera, a filmmaker whose 2003 documentary, "Grupo UniÛn," follows the activities of an association based in Newburgh, N.Y. "Then they start to do more and come into conflict with local authorities."

Magdaleno Bonilla, 35, and his friends wanted to build a wall in their town, San Miguel Tlaltepexi, also in Puebla, that would keep out floodwaters. Mr. Bonilla, who lives in Queens, said the town authorities did not seem very enthusiastic about the project.

"They say to us, 'You don't have the right to decide, you are not here,' " Mr. Bonilla said. Yet, he said, when it comes time for the town's annual festival for its patron saint, they invariably receive pleas for money.

So Mr. Bonilla and his friends formed a committee. Then a New York City organization called Casa Puebla, which has close ties to the state government of Puebla, put them in touch with state authorities, bypassing the town leaders. The group also helped them get matching government funds in Mexico. In the end, the wall was built for $120,000, $30,000 of which came from the committee here.

"As a group we were heard," Mr. Bonilla said. "As individuals, no one was going to listen to us."

Mr. Cruz said that the Atopoltitlan committee also had trouble when the president of the town in Mexico wanted a road paved.

But Gumaro Ruiz ZuÒiga, 38, who heads the partner committee in Atopoltitlan, said that the road was not a first priority for many residents. "We talked it over with the state governor, and we let the people in New Jersey know that our principal need was water, and they agreed to support that project instead," Mr. ZuÒiga said in a telephone interview.

Although it strained relations with the town's president, the Atopoltitlan committee switched its focus to the water project. So far, it has paid $33,000 to drill the well and is applying for matching funds to install a pump and lay pipes.

Mexicans in hometown associations agree that their financial contributions give them a voice that they did not always have when they lived in Mexico.

"If we didn't contribute, it wouldn't have been done," said Dr. Gabriel RincÛn, a dentist in Sunset Park, Brooklyn, who in 2000 started the Mixteca Organization, which raised $15,000 to bring drinking water to Chiautla de Tapia.

But as this fund-raising is prodding greater attention from local governments back home, officials in Mexico are trying to steer efforts toward projects with a lasting effect.

"Painting the church doesn't cost a lot of money and is very visible," said Luis Eduardo Siliceo, a state coordinator in Puebla for the federal agency that administers the program of matching funds. "But our aim is to steer the migrants towards projects that have a greater public benefit."

As migrants in New York become more active in working on projects in Mexico, the delicate negotiations are likely to become more complex. But those who participate in the hometown associations say that their motivations remain, at heart, very simple.

"The town is like one's mother," Mr. Cruz said. "You want to offer your help."